There is one potential way to "make" money on buying a boat.......ot saying you will pull this off or not. One person on here is sort of doing that right now, that is to find an older woody, that needs work, find a buyer up front who is willing to pay you to do the work. Otherwise, as mentioned, not sure a classic plastic yacht will succeed in this type of investment/idea. There are probably one or two boats per 100, that you might pull off something similar to the above woody idea, again, you have to find someone willing to pay your time to do the work.
If this is for you, buy what you like, put some time and money into her, enjoy her for a few years, then sell, knowing you time enjoying what you did is the payback per say.
She drives me boat,
I drives me dinghy!