CW5. We have a 2-bed house in Willaston we rent out. We don't try and make a fortune out of the rent (although ROI is rather good these days, even on a below market level rent) and are fortunate we have a good tenant that pays on time, keeps the place reasonable and doesn't cause any trouble. We don't use an agent as the house is not far from where we live and, as you say, the agents take a sizeable chunk and generally do little for it, beyond calling their mates in if any little job needs doing.
When I was working the boat was the only thing that kept me sane through a fairly stressful period. being able to go to the boat at a weekend and go and moor in the middle of nowhere was a lifesaver for me.
if you want my advice (and of course you don't have to take it) then go for it, buy the boat, enjoy it. As for renting/lodger, for a single young person I can certainly see the benefit of doing it as a lodger, just make sure to stop the night there periodically.
Don't waste any more time! You never now what is around the corner and it might not be what you have planned, so enjoy life while you can.