At a dealer or private? $11K sounds okay but you could possibly do better. Is it a new previous year model? Full warranty on it? What is your TV? I assume you have kids, hence the bunks?
It looks to me that the 1800 is a single axle trailer, 3940 GVWR, 755 CCC, and is 29'-5" long. The CCC seems rather low and I think you could easily end up loading it close to the GVWR, or even over if not watching the weight. If it has a 3500 lb axle, it could be running close to or potentially even over capacity which is not good - you want some reserve capacity. What tires does it have and what is the load rating? Without seeing the TT and having more info., I would want a 4000 lb axle on it. One full tank of water would add 255 lbs. The weight of things you load into the TT will probably be in the 500-1,000 lb range.
Some things I note from Keystone's website: the fridge is an under-counter model and small. One single 20 lb propane tank. Pass-through storage door is very small. Where would a TV get mounted and where to view from? Dinette seating won't seat 4? No sink/vanity in bathroom. No curtain between bed area and the rest of the TT. Full walk-around beds are normally preferable. If you have a flat tire or blowout, you may end up with more damage compared to a dual axle.
I would suggest looking at dual axle TTs.
The parent company to Keystone is Thor so Thor should be included on your web searches. They like to add a few more visible features and bling, but underneath everything is where they cut down on costs. Buying any TT is also about how the dealer and factory deal with warranty issues.
Friends of ours have a new Keystone and it looks nice, but I have not had a really close look at it yet. We used to own a 20' Coachmen Catalina with a 5K lb GVWR and it had dual axles, 6 cu. ft. fridge, good interior and exterior storage space, vanity in bathroom, dual 30lb propane tanks. Within a year, we found the TT to be too cramped and there was no sofa to watch TV from.
If it were me, I'd be looking at some other makes and models. But if you are restricted by your TV payload/tow capacity, that will narrow down choices.