My father was a successful handicapper, and I followed in his footsteps. I made enough money to start a very successful high tech business, which I sold in 1990.
Here's the secret. The horses are actually secondary to the betting game. The odds board is much more important. Bet the odds board, not the horse.
Example: Don't bet horses that are even money or worse - EVER! Not even if they couldn't loose if they fell down out of the gate.
Always look for the 'over-lay,' a horse who's odds are higher than they should be.
Also, become specialized in certain types of races, routes vs. sprints, or grass vs. dirt.
Then, create a stable of horses, and track them like a hawk. Bet them. When they loose, bet them back, but double the bet. Keep doubling the bet until they win.
Cull horses from your stable like a baseball manager changes players on the roster.
Sometimes, when a favorite is not betable, look for the second horse possibilities and play the exactas. But DO NOT bet the horse you absolutely know will win if the odds are too low. That is a fools game. You'll need 4-5 winners a day just to break even betting favorites.
There you go. I lifetime's worth of experience.
Oh, and by the way, its still an 8-10 hour day if you do it propely. Otherwise, save your money or have fun spending it, but don't count on making easy money.