Financed the sale
of a previous boat many years ago, but no longer have an electronic copy of the agreement. Also lending laws, and repo laws, vary by venue so best to get a local attorney rather than playing attorney yourself.
Get a background/credit check as part of the process...you may be surprised what pops up...better before than after. The attorney can also do this for you.
Worked out OK for me, but financing a crusing boat could obviously be problematic if its half way around the world when you need to repo.
If you go down this path, and there are plenty of good reasons not to, then maintain a good relationship with the buyer. In my case the buyer fell on hard times a few years into it. Rather than bailing on me and/or dumping the boat, he called me up and explained the situation. I worked with him to help get the boat sold and it worked out fine for both of us.