I would really scout out where you plan to keep the van day-to-day before even getting close to buying one. I went to USC and daydreamed about living in an SMB instead of a dorm. Couple of hurdles based on my research, though your school may be different.
1. Most parking around campus is in a garage, usually with only a 6'-7' clearance. That rules out Sprinter-style vans and anything with a fixed top. I think only the older Dodge vans are this short.
2. Campus parking rules explicitly forbid sleeping in your vehicle. Parking attendants always patrol the lots looking for vehicles without permits and would start to notice you coming in and out of the van.
3. Overnight street parking can be tricky depending on meters, time restrictions and street sweeping days. And as of this year, sleeping in cars or RVs is prohibited
overnight in residential areas and at all times near schools, day cares and parks. I know this would have ruled out pretty much the entire area around my campus.
4. There aren't many places in a city to dump/refill tanks or recharge house batteries. You would have to be extremely conservative with water and either idle the engine or run the generator for power. Same problem with air conditioning, but less of an issue if you have indoor places to go for the day.
So you either have to roll the dice with parking illegally, or drive out to sketchy industrial areas every night. I think it would be just too much uncertainty for me.