With an inexpensive boat I would consider it. As long as I'm insured from all angles.
I'm not sure I consider a Bristol 38.8 "inexpensive", but that's just me. If you have a fallout, who's to say how complicated things could get.
Have you considered other things like access to the mooring, parking, dink storage, etc. Do you need shore access from their real estate? If so, how are they gonna feel when four of your buddies show up in separate cars to go sailing and need a place to park? Are you gonna be parking on his property late at night/early?
Paying for a mooring at a marina offers possible:
A place to tie up to do repairs, top off the batteries
parking for your buddies when you go out for a sail
Sorry to say it but yea, it ain't cheap, you just purchased a 38ft sailboat, what where you thinking?
I live in New England so I feel your pain, but there are Marinas in Portsmouth...lol