How can people afford rent in big cities nowadays ?

This is true for even small cities like ours which is only about 40K. We have our state university here and the only way for college kids to rent is to have about 8 ea. in a sleazy rental house or 4 ea. in a 2 bedroom apartment. Folks that work at fast food places making $20 - $25 / hr. can't afford to rent unless they are overloading the apartments with room mates.