Is there a game limit to the number of homeless sims generated?

Saving them to your Library doesn't really do anything unless you use MCCC and have it populate from your Library. The game doesn't generate the same sims for every save. It's completely random, as far as I know. You don't have to waste your time giving them all makeovers and saving them, unless that's how you prefer to play the game. I usually leave them alone or delete them.