Thanks for the information but it doesn't make sense that the tow capacity would have anything to do with the weight of the tow vehicle. I can't reasonably imagine that they would rate a MH to tow 5000 lbs and then you have to figure and subtract the weight of fuel, fresh water, black water, gray water, propane, cargo, passengers etc.
For instance a pick-up truck is sold with a tow rating of "X" lbs. I don't think you would have to then subtract the weight of 4-250 lb passengers and a load of stone in the bed to determine whether or not you can tow a backhoe to a job site.
That said. I know zero about this subject and am deferring to those who know much more than I but, common sense (to me anyway), would seem that the tow rating would be based on a nearly fully loaded tow vehicle.
Curb weight of the Bronco Sport Big Bend model (the one we are looking at) is just under 3500 lbs. so a 1500 lb. trailer should squeak me by. We plan on staying in the southern half of the US so mountain climbing won't be an issue.