For the house exterrior I'd go with an airless, and find something to practice on first, like the neighbors car if you aren't good friends
, but probably not a good idea... If you contact the local hazerdous waste facility they can probably get you some junk paint to practice with...
As far as a power washer, be ready to spend $400-700 for a descent one, DO NOT get one with an adjustable tip, I won't go into details, but that tip reduses the power of the washer so much you might as well put a nozel on your garden hose, get one with several different tips that can be interchanged for a different cleaning pattern, an air compressor will not be good enough...refer back to hose/nozel statement...