Do I have to buy a lot of machines, or can I just purchase one?

Yes, you can buy as little or as many machines as you like. There is no minimum purchase.
 

How fast can I see a return on my investment?

Depending on the traffic at your locations, you will start seeing an income immediately.
 

Do these machines use a standard household outlet?

Yes, they use a standard 110 outlet.
 

Do I have to give the location any profits?

It is usually standard to give the location 10% of the net profits because you are using their electricity, but most times they are just happy to have your machine there for their employees.