There's a bank on base with an ATM and they can withdraw money as needed. NAPS education is free, as is room and board. Their pay more than covers their expenses, but not by a whole lot. Some parents pay the uniform and books costs and let the kids live on their pay. Some suppliment the pay checks and let the kids pay expenses.
Many kids are on their own.
How folks work this out is up to families and their own financial situations. Do what you are comfortable doing. There is parking. NAPSters really like having the ability to get away on the weekends. There are storage facilities and bikes are useful most of the year.