OP, we got a Mercantile Marine Loan to cover part of a purchase some years ago now (paid off). It worked well and didn't cost the earth. That said I wouldn't do that if your over 45 as it puts pressure on life a little more, in my opinion. Younger maybe better for large credit.
Mooring is going to be the thing that will probably be a hitch, especially as you'll need it close to your work, I would think. I hope you do find somewhere if you decide to go ahead and follow this path.
Living on a narrowboat is great, but as with any living it has its drawbacks. Where your moored could make the difference between a good experience or bad. Pathed walkways, handy waste disposal & water point, mains power if you want that etc. With a good mooring, life could be quite nice on a boat, at the end of a farmers field, well not so nice,, we've been there and done that (never again).
Living on a boat is good, we did it for a number of years, we don't live onboard anymore and probably at our age not choose to do so now. But life without access to a boat is pretty miserable for us. That is why we keep a smaller boat now, justt to keep our hand in.
OP good luck either way.