To continue ...
I've been using my own customized version of this
Towing Capacity Worksheet (in .xls format) for years now to accurately determine just what the various vehicles I've owned over the years can safely tow within their rated limits. This worksheet does exactly the same thing one can do manually with a calculator and the results are the same either way.


Shocking as it may seem this clearly shows that my 1/2 ton Silverado which has a real world payload capacity (as equipped) of 1400 lbs uses pretty well all of that capacity to tow a trailer weighing less than 5000 lbs. :E Shocking, I know, but yes this is sadly correct - payload capacity is and always will be the mitigating factor when determining just what any given vehicle can safely tow within it's rated limits. Back on Page 2 the OP said -
"My tow vehicle is a 2008 Nissan Xterra 4WD. It has a 6cyl. 4 liter engine", in which case the situation will be even worse if for no other reason than lack of sufficient payload capacity. :( It's easy for keyboard pundits to claim otherwise but the numbers don't lie - if as you said earlier
"First, I'm looking for something in the 22-24 foot range, & under 3500 lbs dry weight" I can absolutely guarantee you'll be sorely disappointed with the results, particularly if what you find in the used market also has a slide which will only add even more weight and worsen the situation even further.
Good luck with whatever you do choose. :)