I have a 2001 Exiss XT308MT so very similar to that trailer but my is a 3 horse with a midtack...same length as your trailer but mine has a mid tack where yours has a 4th stall.  Mine has a factory LQ done by NuWay which is probably the same as your trailer.

I bought mine 2 years ago for $17,500 and I would like to think I got a pretty good deal.  It is in good shape, I have done a lot to it just because it's my toy.  Nothing major but a lot of little things like changing outside vents that were faded, cleaning everything really well, etc.

I think the biggest concern with a trailer as old as mine and the one you are considering is that all of the appliances are getting old and if you can't fix or replace it yourself it's not a stretch to think things like an AC, Furnace, Fridge, hot water heater, etc could all cost $500 to a $1000 each to repair or replace.  The fact that your ex lived in the trailer would me it has been well used.

With all that said I looked at trailers for a long time and it's very difficult to find much under $20,000 and actually now that I have cleaned mine up and decorated the interior a bit I would say it is comparable in look and function to many of the $25,000 to $30,000 trailers I see.

I would say if you could buy the trailer for anything under $20,000 you would probably do ok.