x2 on the tires; ten year old tires on front are an accident waiting to happen, and 7 year old tires are also due for replacement. They probably would get you home fine, but I would not recommend high speed (interstate/freeway) or long distance travel on them.
I looked at one Gulfstream Ultra when I was shopping around last year. The layout on that one was ideal for what I wanted (and rather unique—it had bunks and a second dinette in the back, rather than a queen bed), but that particular unit had been neglected for some years and had massive water damage throughout. Gulfstream was reasonable quality so far as I know—definitely not bottom of the barrel, nor head and shoulders above the rest, but decent overall. They're not making motorhomes anymore (just trailers), but do appear to have some factory support still for the older products.
$22K might be a fair price if it's in really nice shape and condition and has been well maintained. The old tires do not bode especially well on that front in my mind, though; someone who neglects tires may also neglect roof seam sealing and other such tasks. It's hard saying without looking.
Do check out the manufacturer's weight statement to see how much carrying capacity you have (or, better yet, weigh the actual unit). With two slides and a fairly long house, it could well have little capacity left for water and stuff and people.
