Agree there are (too) many pitfalls in trying to generate a direct income via AirBnB or similar.
But haven't some hire companies had arrangements in the past whereby they lease a boat from the owner and then hire it out? During peak season they can effectively increase the size of their fleet without the upfront purchase cost; generate some income for both themselves and the owner; and deal with the rental, changeover, servicing, emergency call outs etc. No idea if it still happens, or how it works in detail so whether it is practical.
Clearly you have to be prepared for the boat to be moved; you have to be moored near the hire base; you might have to move out for a week, or weeks, at a time; and it restricts the amount of personalisation you can do - it might have to be a lot more spartan than most people would like for their home. But for the right size of boat, renting to say couples rather than groups, and if there is no other way for your finances to work, it could be worth looking into.