[Crazy Dazz]

Chains should hold it off the ground.
Depends on length, where there are attached, and the height.
The problem is usually with overriders, with the chains attached quite far back, and consequently too long. Put that on a low sedan, sagging at the rear, and yes, once the chains go vertical, the tow hitch will be hitting the ground.

air-shocks are good cheap & easy fix, especially since you can deflate them when not needed. They don't reduce the load much, but do help keep it level, and help your car handle the load.
(Compared to an extreme sag, by levelling the load they do put a bit more onto the front and onto the trailer axle(s))