When I did boats, my employers typically charged per foot. There a per foot price for HULLS and a per foot price for TOP SIDES. For Hulls, obviously these were done when the boat was pulled (Typically spring or fall unless it was pulled for maintance).
Hulls are super easy. I enjoyed doing them as long as they were chocked really low and I didn't need a ladder. If you have a helper lay some compund on just ahead of you, you can bang out a hull really fast! FOr teh most part hulls are smooth easy pieces. The transom was the biggest biotch with the cables from the loran, motors if outboards, swim platforms...etc, but nothing too bad.
Doing teak is a PITA but not very hard either. The chemicals to do it right are expensive and if you want it to look killer, you need to sand it smooth before sealing with oil. Always oil the teak after you seal the gelcoat and for best results & allow the teak to dry fully (Sometimes we would go back a day or 2 later to do the teak) before oiling).
I think boats could be a very lucrative field for many of you guys. One guy I worked for got a contract with a huge marina and that was enough work for him and up to 6-8 guys. He would sell weekly washes, wash n wax, etc.
Interiors aren't as hard as they appear. 3M gum and adhesive eliminated just about every problem. ALso, scrubbing the vinyl with a scotchbrite pad and an APC worked wonders on the vinyl pieces. Believe it or not, a very good wash took care of most of the work. Just need to be careful of not getting wax on non-skid surfaces, not hitting the smooth gelcoat with the scotchbrite pads, and be sure to lift all the hatches and clean those out! Think of them as the wheels wells of cars! LOL
Figure it this way, if you do 1 boat for about $400-600 and it takes a full day, you would need at least 2 if not 3 cars to get the same. Only thing with a boat is you will need a helper as it more than cuts the time in half! My boss was the biggest tool and he made a ton of money.