We have the rig in our signature. Fully loaded the rig weighs about 21,000-21,500 lbs. and our Honda Odyssey weighs in at just under 4,500 lbs.
Roughly speaking, we probably see a 0.5 mpg decrease in fuel efficiency, and we average about 7.0 mpg-8.5 mpg depending upon generator/AC use, terrain and speed.
We use a brake system and don't notice any difference in stopping ability. However, I can tell feel the Odyssey back there when trying to accelerate. The RV is feels peppier (if you can use that word with a motorhome) when the Odyssey is not connected. But as I said, with the Silent Partner Braking System, I really don't notice any difference in stopping ability when towing.
The cost while travelling is probably a non-issue. The major expense is the initial set-up. If you're handy and can do that on your own, then you can save some $$$.
~Rick