A common discussion I see on twitter and elsewhere has to do with whether it is possible for someone just starting out to make a living in sports betting. I personally had a full-time job when I started out in betting and I would recommend others do the same; however this may not be an option for everyone. I was fortunate to have a job that allowed me free time and flexibility to work on my betting models. In addition part of my job was to better understand statistics and the markets, which meant that I was getting paid to become a better sports bettor, and I didn't even have to win any bets to do so.
Having started out with around a $2000 bankroll deposited online, I spent about a year losing, then after that made more than an average Western middle class salary each year. So I think it is definitely doable for someone with a small bankroll but the skills to win - and this is really important, because most people don't have the skills to win - to make a living at sports betting.
The most important advice possible I can give to someone just starting out with a small bankroll, say in the mid four-figure range, is to only bet the smallest markets possible. That is, bet markets such that the max bet offered at a reasonable sportsbook that pays out if you win is less than say 10% of your bankroll. If you have a very small bankroll this isn't really possible, so just stick to stuff where the max bet is $500 or less. Betting any market bigger than this simply makes no sense for the following reason - the bigger the max bet possible on game day, the tougher that sport is going to be to beat. The US major sports and soccer all get big action and have major profit/loss impacts for the sportsbooks. No book is going to take five or six figure wagers on a sport where they consistently are offering 5 or 10% edges to the bettor. Even if it is a heavily bet sport, the books usually can't get enough recreational action to balance the max bets coming in from winning sharps. What this means is that they are going to put up mostly decent opening lines where there isn't a big edge to be had, sharp bettors are further going to hammer these edges away, and by the day of the game the maximum realistic ROI you can hope to attain is going to be in the low single digits. For someone starting out this is not going to be much fun as the return on your time will be very low, and the variance huge.
Contrast this to many small sports. For the same reasons big sports are tough to beat, small sports are soft and easy to beat. The top sports bettors in the world simply aren't going to waste their time betting on a sport where at most they might be able to scrape together $1000 worth of action before they completely ruin their odds. Even though they might be able to attain an edge in the 10% range, that is still only $100 a play. While that sounds like a lot of money, once you really get going at sports betting, your bankroll can snowball out of control to the point where $100 is not worth your time. As a result, sharp sports bettors come and go from these leagues - some just starting out will build a bankroll from them, but the bettors that do very well tend to move on to bigger and better things.
Furthermore, there are limitations at the firms who produce the opening lines in these sports. Contrary to popular belief, Pinnacle or any other sharp sportsbook does not post the lines in most of these tiny sports, they just copy what is offered elsewhere at the time they decide to open the market, which usually comes from a few small firms based in Europe. There are only so many people in the world who can handicap sports well and a lot of them are making way more money betting the plays they handicap than any company can pay them. As a result these firms tend to be poorly-staffed, and the few who work for them who can put together very strong opening lines tend to be assigned to the larger sports, leaving the new guys and b-teamers to post the openers in these tiny sports. The models they use to produce the opening line are extremely basic and easy to beat, but this is not a big deal for the sportsbooks as limits are low and they can quickly move the line to prevent further losses; meanwhile they take decent action from recreational bettors on these games who pick games at worse than random allowing them to turn a profit. The combination of poor opening lines and lack of competition from sharp bettors means small sports tend to stay fairly soft.
I am going to provide a concrete example from a league I made a lot on when I was just starting out, the DEL2, which for those of you who don't know, is the second division ice hockey league in Germany. I just picked a game at random from oddsportal here and honestly, this was the first game I looked at. You can see in this particular game there was an over 50 point line move from open to close on the over 5.5 at Pinnacle. From my experience, this type of line move in a tiny hockey league is very unlikely to be from any kind of breaking information; it is much more likely that the books simply put out a bad line and sharps hammered them. Such a line move suggests the first bettor had an edge in the 15-20% range and these types of moves are extremely common in these small sports. The limit at the time they made this bet was likely $100 or $200; a profit of $30 a play can easily pay the bills if you are just starting out.
The great thing about small sports is that there tend to be a lot of leagues around the world offering the sport, and the same handicapping methodology tends to apply regardless of league. So if you can win in one league, usually you can also win in another similar sized league in the same sport (although be careful, even some small leagues are dirty to the point that they are hard to beat).
Daily player props on major US sports are also a great option as well for new bettors. The sportsbooks do a notoriously poor job of pricing these props and there are dozens of them to bet on any one day of US major sports action. So the new bettor gets the opportunity to have a nice edge on many different plays in any one day, allowing them to put their entire bankroll in action across many plays without having to bet an unreasonable percentage on any single play. These were where I really built my bankroll starting out, having had some incredible runs including making over 100% of my bankroll in one day, despite never betting more than 5% on any one play. My understanding is that nowadays these are still very soft, but quite a lot tougher to bet than they used to be, with many sportsbooks cutting off accounts after just a single day of betting props. Still, if you are betting very small you probably can bet these for a while before they stop taking your action.
Small sports aside, the other important aspect of making it as a new sports bettor is living in a location where you will have good access to all the major sportsbooks while also having a reasonable cost of living. Of course, you don't need to actually live or be in a given country to be able to bet from that country nowadays; it is a straightforward exercise to find someone in Canada or whatever other country with a Pinnacle/betfair/other account and TeamViewer in to place bets from their computer. But in my personal experience it is much better to control the accounts and money yourself whenever possible, as fewer payment issues can arise in this situation. Furthermore, while you shouldn't have any problems as a mere bettor, there are always legal questions around sports betting in the US.
Many people mention Las Vegas as a good choice for the aspiring sports bettor, but I think it is terrible for this purpose. Las Vegas still does have a lot of sportsbooks, some with unique lines, and while a lot of them suck for big bettors, they will all have no problems taking action from a new sports bettor who bets a few hundred dollars per game. The problem with Las Vegas is that the books only offer US major sports, don't usually offer props, usually price at -110 except in baseball, and generally wait to post lines until the lines have stabilized at Pinnacle and CRIS. In other words, they don't offer any of the best betting options for the up and coming sports bettor; this is of course by design, as they wouldn't get much recreational action on small markets and have no interest in offering anything that is potentially unprofitable. What this means is that Vegas is pretty much useless unless you are looking to bet big on US major sports, in particular football.
While there are some great opportunities to bet through "pay-per-head" books in the US, in my opinion, if you are from the US you are likely best off moving out of the country to bet full-time to a country where online betting is fully legal or at least unregulated. This is not as easy as it sounds any longer as a lot of countries have shut out "unregulated" sportsbooks, which usually tend to be the best books to bet at as they take the most action and biggest risks. A side benefit of moving offshore is that such betting is tax-free for citizens from most countries; US nationals must pay taxes on offshore income but get a ~$100k exemption if they stay overseas for all but 30 days out of a calendar year.
For those in the US, I would say Mexico would be the best option. All the best books allow Mexican customers, and while Mexico can certainly be violent and dangerous there are areas in Mexico that are far safer than, for example, Las Vegas, and one can live very well in those areas making as little as say $500 per month. Mexico also has a pretty relaxed visa policy; you get six months per entry and visa runs are not really a problem. It is also fairly straightforward to get documents and banking access to prove to the sportsbooks that you are legitimately living in Mexico. Costa Rica is another decent option and is fairly similar to Mexico. Canada used to be good, but nowadays it is somewhat difficult to get set up for banking and the visa policy there is not as favorable; in particular they take a negative view of visa runs as well as people staying there for a 2-3 month period to bet or play poker.
For those in Europe the best places to bet are mostly in Central and Eastern Europe. While the Schengen-area countries (the exception is Austria) have mostly regulated gambling meaning the top offshore books are shut out, if you cross the border you can still play at almost all sites, plus these countries tend to have a lower cost of living. I have spent time in many of these countries myself and would consider them very nice places to live (at least compared to the US which is mostly a shithole), although perhaps unpleasant in the winter.
The number of people out there with both the skills to beat sports and the willingness to do whatever it takes to get action down has to be fairly low which is why there aren't many professional sports bettors out there. So as many have said, of those starting out, almost all will fail. But it is definitely possible and a great lifestyle for those who have what it takes.