Sounds like a good deal to me. Thank goodness it isn't on the east coast or I'd be severely tempted.
I fulltime in a 25 FB SE - and for a family of four - with kids on the cusp of being teenagers, you will want the extra 2 feet. The pantry and closet space alond will be a godsend. Parking a 27 vs a 25 isn't a big deal. Finding big enough gas stations may be, so considering a diesel vehicle and using truck stops may be your choice.
This unit has awnings all the way around, an extra $2000 by itself.
Now the 2010's should be coming out shorty... so get in writing that you'll still have a factory warranty for 2 years from your purchase.
Look at the unit. There may be a few filoform issues (make them throw in a can of the spray that stops it cold - it works.) IMHO, it actually anodyzes the little white lines which stops it. The new clearcoat is put on at the factory, so the cut edges are raw aluminum. If they are treated immediately, no filoform. Why they just don't do it at the factory?
Do check the floor perimeter carefully - even a new unit can have a leak - and in a wet climate, minor amounts of water between the inside and outside shells could damage the floor. The rear window is a particular place of interest.
Of course with an asking price of 50K, you could always try a slightly lower offer. But it is priced aggressively against a new 2009 one (check www.colonialairstream.com