I do this through the services of a professional charter
If you wish to do it on your own, one of the first steps I'd recommend is talking to your insurance company about the liability and insurance implications and costs associated with such a venture.
Also does your friend the sailing instructor have his Captain's license
? (Assuming you are in U.S. waters and in waters where it's necessary.)
I recently purchased another boat I let a friend use, and that reminds me of the the importance of talking though and putting in writing the financial implications of boat sharing. Who's financially responsible if your friend the captain
, hits a reef or runs the engine
I'll add that I agree with Ram, that when people know there is insurance money
to be had, the lawyers come out of nowhere. However, I've also seen people who are uninsured or underinsured have their lives ruined from being sued. Sometimes a pissed off wife of a dead client doesn't care about the money or any risks her husband may have knowingly assumed. She just wants to see someone pay.