Very nice, and a very nice price. I got my K3 in 2001 for $200 US and those deals are all gone now, these bikes easily go for 800-1000 in the shape yours and mine arrived in. How's that fueltank? it looks great but is it rusty inside or underneath? I noticed it still has the chrome trim at the bottom edge, those are a bit rare in good shape so care for them well. Your seat doesn't look original, but if you like it, it's fine. Seats are available from a few sources, including Honda. There aren't too many parts that aren't available somewhere. Check your local classifieds, craigslist, look in peoples backyards and garages as you drive by, ask friends and neighbors, parts and other neglected bikes that you can use for parts are out there waiting for a caring hand to redeem their value.
But it can be addicting, you may not be able to stop with just one bike.... a word about tires, old tires get hard and crack with age. They aren't safe to ride on, so read some of the threads here about tires and figure out how much you'd budget for good tires. Oh and beware of posting questions about tires or oil, it's sort of a running joke around here...
Welcome.