I thought there was going to be a twist when I read the title but no there is not,you are serious!
So you want to use your 20k to buy a boat to live the dream but have the system pay rent for it!
When I was unemployed and had the system paying my rent I had to live in a flat on such a rough estate that the flat was on a so called ''Hard to Let'' list.
No one else wanted to live there, it was so bad I bought an old bedford cf camper van for £500 in a bloody cold november and handed the keys back for the flat.
Just move the boat around and stop taking the mick.