Thanks Elbert, I also don't know what PWC means. If it does mean wet bike/Waverunner there is already a rental business for them. I don't know of any jet skiis here (using the word in its strict meaning - the machines that have no seats and that you stand on).
Any business like this is going to be tough, as the machines are very vulnerable to rough or thoughtless handling and that's just what they get. Most people who rent equipment seem to take it as an opportunity to give it abuse they wouldn't dream of applying to something they own. Impellors are regularly destroyed by sucking in sand or sea grass, and most people dock by feel, often hard enough to break fibreglass.