Would you be purchasing an established location/route, does the corporate office do sales, or would you have to do your own sales?
Who would be responsible for stocking and servicing the machines? What if people get sick from the product - who is responsible for the liability insurance?
In general, vending machines are a pretty good, but they are a lot of work. I would be wary of getting involved with a machine that needs to be stocked daily like a fresh food machine. Depending on how many machines you owned that could be a WOH job. And depending on your local health code, you may not be able to take your kids with you while you service and stock machines if you are responsible for taking care of the machine.