re: Anyone own vending machines?

You would not want to buy many used as the maintence can eat into all of your profits. Go ahead and get one that would run you about 4k. You would also want one that is a stacker machine as they are easier to load and they jam less often.
Also if it does not come with a credit card reader make sure you purchase one, they usually run 300-500 bucks. This can be the difference in a sale or not depending on if they have cash or card.
Find a high traffic area that you know will sell some drinks and set inside. You can use D7 Lead Finder in order to help you find a busy location if they have access to your area or if you are friends with someone who owns a business or you already own a business then you could just place one there. You would need to have a few vending machines to turn a nice profit as one may only bring you a few hundred bucks a month once you account for the beverages you have to buy. Also find a wholeseller to buy your beverages from so that you can buy in bulk.