Re not making money on an old hull, it's not always the case. My now finished (if it ever is 😉) project, restoring a hull of unknown age and provenance, first registered in '68, with a wooden top and roofing felt roof!, is now worth maybe a 1/3 more than I have spent, passed 2 bss, due the 3rd this summer. It has been a labour of love, using recycled materials including some of the innards of a caravan about to be scrapped. The bed units, kitchen unit all prebuilt and lightweight. With a bit of judicious trimming to fit the tumble home, the complete plastic lined bogshed with shower and cassette went in no problem, solid oak flooring throughout, new steel top battened sprayfoamed and lined out, electrickery and gas fitted.
I've no intention of selling it, but if I did I would make a bit of profit.