What we have here is a Yamaha XS1100 'Midnight Special'. It looks like it needs some love and is for sale for $500 along with some extra parts. The flash from the phone makes this '70s bike look pretty disco!
The XS1100 is a late '70s/early '80s 'super' bike. From what I've read it's Yamaha's Vincent Black Shadow. You're spoiled for choice as far as customization goes with the XS1100. It's a big, air cooled engine with the old fashioned dual rear shocks. It begs to be café racered a bit.
As a tear down/rebuild, this makes a pretty good basis for a winter project. It would be my first air cooled bike, as well as my first tear down/rebuild.
The Clymer manual is readily available (I'm finding Haynes manuals lacking in covering many motorcycles). This could be a winter sanity thing.