550s are great all-around bikes; I've had a few including a '75K that I owned for 30 years and a really nice '75F1 that I picked up a couple years ago and have been bringing back to original here in Mexico City.
That bike looks like it's in great shape cosmetically, and with 12k miles it's hardly broken in. If it's been sitting, you'll almost certainly have to clean up the carbs (and keep the original brass, just switch out the seals), although maybe they were drained when parked. Change the oil, 3K mile tune-up and I bet the thing fires up and rides solid. Tires, chain, plugs -- all stuff to replace. See if the gas tank is clean -- if not, could get away with rust removal and worst case scenario might have to line the tank (and be careful of that original paint).
You'll likely have to find an oem headlight bucket, ring and light if you pull the Windjammer, but worth it IMHO -- there are others here who like fairings but not my thing). Sissy bar and sexy do not belong in the same sentence, again, just my opinion.
There is a great Japanese bike junkyard in Phoenix called Bob's (on Elwood, not the Harley Bob's on University although that place has some amazing old bikes too). Unfortunately you missed it's prime by about 2 years -- they have sold off most of the property and kept only a small part of the yard. There are a couple 550s out there but pretty well picked over. There are some 550 parts in the warehouse if you poke around. They also have a shop with a ton of aftermarket and some oem parts (don't buy aftermarket carb or tune-up kits, get the oem stuff if you want your bike to run right). They have cheap tires and cheap mounting prices, but some of those tires are 10+ years old.
First step, get that thing running. Get a manual and read it. Go through the tune up procedure -- points might be just fine as they sit but I'd change out plugs and oil and filter and check that air filter.
Parts alone on that thing are worth some money if they are in as good a condition as they look: original exhaust, original paint tank and side covers, then other stuff like seat and carbs and wheels, etc. What are they asking for it? I looked on PHX craigslist and didn't see it listed. Does it have a title? One thing about AZ (I lived there for 20 years) -- if there is a lost title getting an abandoned vehicle title is super cheap and easy, unlike a lot of other states that will force you to buy an expensive bond.
I imagine if this is being advertised somewhere and is decently priced it'll go quick. If you want it, you should jump on it.
