Ductwork of newer houses is just this accordion plastic stuff. Just rip all the old stuff out, zip tie, duct tape the new stuff in, and viola.

Pool pumps, although expensive are freakin easy.

The gas line will probably be the hardest, and... the cheapest, or the most expensive. Finding the leak is the pain, as it usually require digging (sometimes under the house, where it is not supposed to be...)

But, yeah, that is a nice garage. If i wanted to live in Tucson, i would totally go for it.

Probably all the flippers are saying its too pricey, so have passed.
Good luck.