I would suggest its zoning, zoning, zoning, plus foodservice contracts. The van ain't cheap, unless you're looking at a health department approved used vehicle. Neither is commerical vehicle insurance - you might be in debt for a long time working part time only.
By zoning I mean look at your town's restrictions for this kind of business. There might not be any, but it is more likely there is a commericially zoned area that street vendors are allowed in. At least, don't spend too much money based on assumptions without doing the research of talking to the city management folks.
By "schools" I guess you mean colleges. Secondary schools are not the market for this and are much more restrictive, controlled environments. But the colleges - and secondary schools too - are Big Foodservice Business. Aramark, Servomation, etc, usually have contracts with colleges for exclusive services. Often the main cafeteria, the student union, the little coffeeshop by the library and the vending machines in the dorms are all run by the same foodservice corporation. You see coffee trucks and chinese food vans, etc, near the urban universities but you are thrust back into urban compliance issues, and much fiercer jockeying for location.
On the other hand, your situation might be a gold mine. My reality check is not meant to deflate that idea. However, please remember that a mobile espresso business is as complicated, messy, and hard as any other business once the clear light of day dawns. Regarding your basic question: Unanswerable. How much money can you make running a brick and mortar coffee shop? I guess there would be as many anwers here as registered users.
