I'm really torn. Scooter is the outside cat that I've been feeding and
just had neutered and tested. Perfectly healthy but I can't really
take in another cat and Espy hates this one. Right now, because it's
cold, windy, and rainy, Scooter is in my Cat Introduction Room but
that can't last. He already wants to get out into the rest of the
house. Espy is going nuts and making noises I've never heard before.

I thought about building him some sort of cat house outside for the
winter but I can't figure out how to keep it reasonably warm and dry.
Oh, well there are these things:
http://www.cozycatfurniture.com/cat_houses.html

Some look about right and have optional heat and insulation. But that
sure isn't cheap.

I thought that maybe I could just put a cat door in my garage and let
him live there, but I could end up with a whole colony of cats and
have to neuter them all and/or deal with the kittens. That's a bit
more than I want to deal with.

Any advice?