I honestly don't know anyone who makes a living at gambling. I'm sure there are some out there, but I don't know any.
WIth horses there is just so much information out there that didn't used to be out there. The glory days of betting horses seem to be gone.
Up until the 90's the DRF didn't publish general trainer stats, much less the detailed ones they publish now. Trainer switches would show up and they weren't published either. You culd make a score off a switch that not everyone knew about it or remembered.
Tg and rag didnt used to be mass marketed like they are now. The internet made them easy to mass market, those numbers used to be worth their weight in gold to those who had them. The DRF used to publish archaic speed figures and now they publish Beyers. Wet track, turf, and sitance lifetime pp's aer now published. You used to have an edge if you cold remember what the horse had done on those surfaces outside the races shown in the DRF. Jockey stats didn't used to be published, those little sidebar columns that tell you who is a half brother to who didn't used to be published, and even sales prices didnt used to be published.
Used to be able to save the DRF's and look up workouts and see how fast they actually were. You could go back and chck a certain date and see a horse had the 2nd fastest work out of a big group, and now that info is all in there for anyone who has 5 bucks for a DRF. Theres no more information edge, everyone has all the info that wiseguys used to work hard to keep.
Heck even trip notes have become diminished in value. Now everyone has race replays.com, brisbet, etc. You can go back and watch any race with a few mouse clicks and see what kinda trip a horse had.
You've also got sharks chasing other sharks now most of the year except on big days when you get the "sucker money" like Derby and BC.
The game has changed and its a very hard one.
I made two scores(no surprise on BC day and Derby day, they would have paid less than half that on a regular pool day) and caught a percentage of a couple nice pik-6's. Thats about it, my every day playing was definitely in the red ink, and only those few scores kept me above water, and even then just barely.
If you are gonna play full time today for a "living" you need a big bankroll, even more patience than ever before, and need to work constantly, and I mean constantly. You'd probably have to put in 100 hour weeks and still need to get lucky to win enough to be considered "a living".