I've been kicking around this idea as well. I want to start something that I can do with my kids that they can eventually take over. The sole purpose is to fund their schooling and it also gives them experience running and growing a business. Learning these skills will leave them with the ability to be able to support themselves and be self reliant. I have thought about some type of food truck.
I thought about starting small with something like snow cones that would be cheap to start. You could use either a simple trailer or even a portable canopy and a few folding tables etc.
Eventually though I think you have to have something unique to separate yourself from the competition. I spoke to a lady who ones a dip and dots and she cleared $8000.00 in three days at a balloon festival! That is unique though.
I also thought about a T shirt business where you could do screen printing and also sell your own designed shirts. Still kicking things around.
Keep us post d on how things developed for you. I would love to hear about it.