I did bulk vending when I was in high school. It was fun actually. First I placed machines in all of my families works and friends business and ran those. Made quite a bit of money and it was all cash. The bank started to get angry with all of the quarters after awhile though...
The hardest part was changing out the machines and keeping candy fresh. Luckily all of my machines were in office locations so they rarely got messed with but a lot of kids put smaller money in them and tried to scam me but the machines just ate it.
It's hard to find good locations. Most of them are taken either by big vending companies or local stores that have placed their own machines.