As someone who owns a castle/manor house and desperately wanting to sell it... I agree completely. At least theres normally no property taxes on listed buildings, but just keeping it from falling apart is enough to eat a moderate income.
Very easy to say, but would require multiple years worth of salary for me to open that, and the location is not suited to a museum. A wedding venue maybe, but still the investment required to start that is beyond what I can do. I also do not want to quit my software career in London to bank everything on a hospitality business in the middle of nowhere in Eastern Europe.
Lots of these places do just that -- but unless you want your job to be "I run a tourist attraction/wedding venue as a small business", you might prefer to sell the place and let somebody else do it...
As many startups realize when the investor’s money runs out, getting revenue isn’t sufficient.
I guess making the revenue pay for the investments in art, maintenance of the building, security, etc. and buying you clothing and food is left as an exercise for the reader.
Art would be $10-30k. No need to go overboard. Get some exhibits about local culture or something like that. Screw that, get some cool shit made by some online blacksmiths or woodworkers. Put a bunch of placards about the history of the place. Security isn't a big deal if you don't have much of value.
More importantly, make sure this is a passive business of sorts. Works well if you live in or near the same place.