plash3,
I don't have quite as jaundiced a view as Midlo Dad, but on the other hand..... I don't have a son playing collegiate baseball.
Anyway, for D1 colleges, the information is provided in Bylaw 17. You really only need to read 17.0, 17.1, and 17.4. In round numbers, about 12 pages! Pay attention to the definitions of countable athletic activities, and voluntary activities. Make sure to read 17.1.6.2.3, which is baseball specific.
Note that some of the rules are not easily enforced. For example, 17.02.13 covers voluntary activities, and says that there can be no penalty for not participating, and the monitoring staff cannot report attendance to the coach. Yet, I guess that if Player A does the voluntary activity and Player B doesn't, the coach will be able to sense that somehow.
And so most players will work on baseball quite a bit more than 20 hours per week, while the college president can sleep well at night, knowing that the players aren't required to do more than 20.
NCAA Division Manuals