I think the first thing you need to do is talk to the charter companies you are interested in having your boat with and finding out what boats they accept under what conditions. I think you will find most don't just take what ever boats people want to put into charter. They have certain boats they want to carry and want to make available for certain amounts of time.
Some companies offer a guaranteed income
from charter, others give you a percent. Going with a percent may allow you to actually make a profit, but you may also loose money
if it's not rented as much as you hope, especially if you are responsible for slip fees
, etc. You mentioned one boat that made a net profit, but I've read reports of many people who hoped to make a profit and lost
as much as well under percentage programs.
I think your idea of sharing the costs of boat ownership
is a sound one. If you only use a boat one month a year, divides the costs much more than it creates additional costs at little increased cost. This is same strategy that makes charter management work.
Realize that many of the charter companies offer fractional ownership packages and have already worked the logistics and legalities out. I currently have a boat in charter management. It's much cheaper than owning it outright myself. It's also much, much cheaper than chartering. I figure I use my boat about 5 weeks per year for the cost of a 7-10 day charter. The advantage compared to fractional ownership is that I don't have to fight with anyone else over time use. I get it when ever I want. The advantage of going 100% with fractional ownership is you don't have Joe Public using your boat.
If you go about it yourself with friends think carefully about what you will do when someone wants to leave the partnership
and also the finances in the end. I think it's the issues associated with the sale
in the end that can make all the difference.