> bootstrapped startups from underprivileged people.

i dont think startups should be paying a retainer. You do this only after it's worth the money - ala, you either know your domain is a gray area and is definitely going to require a lawyer.

This has nothing to do with underprivileged people or not.

This might depend on where you are. In my area, it's unusual to have to provide a retainer at all unless you're doing something big or the lawyer suspects you might have trouble paying your bill later.