Comment by bell-cot
You'd really want a siding with (RR-specific) electrical connections, no noisy/smelly industry next to you, decent views, an elevated platform, and some parking spaces.
They're darn rare, but do exist. If I was Old Money, I'd probably build more in a few in beautiful spots - and freely loan 'em to my peers, as a social networking thing.
There are houseboats as well.