Since I start out in blank hoods, I use Uni as an opportunity to make as much cash as possible in as many ways as possible, then store it in the form of inventory objects so my Sims can take it all with them back to the hood and build a nice house straight away on a blank lot.
Right now I'm starting my favourite Sim over again as a (orphaned) teen who lives on her own. I made her as an adult, aged her down on the lot and the game told me she couldn't go to college yet because her school grade was D- ! 0_0 So I used that as an additional opportunity to get her making money and getting her grades up to A+. By the time I moved her into college, she had racked up §28000 in household funds and an additional §6000 in scholarships. I'll keep her busy making insane amounts of money in college and getting on the Dean's List, but I'll use some of the suggestions in this thread to let her live a little.
If you use boolprop to age down to teen/child, their grade starts out as an F...I aged an adult down to child once and she got taken away by the Social Worker FIRST THING! (And yes there were adults on the lot.)
I'd use something like SimBlender for that, then they start with the normal C grade.