My dolly has surge brakes and they work fine. If the dolly tries to "push" the MH, the pressure will push on a brake "master cylinder" mounted on the hitch which will apply the brakes on the dolly. The harder you brake the MH, the more the dolly tries to push, and the more the surge brakes get applied.
If you buy the used dolly, replace the brake fluid, bleed the brakes and check their adjustment just to be safe. Put about 7000 miles on mine this year, about half on surface roads, as opposed to interstate highways, with no problems.