Under 100' for me. Although I'll qualify that statement with two points;
1/. I haven't done much in years as I've been flying transport cat jets. When I was teaching/doing them regularly it was in PNG where we had a proper low level training area. Upper limit 1000'/lower limit don't hit nuffing
2/. Lately I have done a few in my A36 Bonanza to get current again and yesterday did one to touch down at my home field, YRED.
IMHO the banishing of proper Low Level training areas in Australia (and the UK by the sounds of it) over 20 years ago was a retrograde step.
In D904 near Port Moresby we could and did go below 50'..when we weren't chasing villagers or making them get out of their duggout canoes/Banana boats
Chuck.