Obstacle clearance at MDA on a non-precision approach is 300 feet ... and you would have to go to the TERPS, I believe, to find this out. Unless, of course, you did what I did ... I looked at the chart for the localizer approach at the airport where I used to teach ... there was a tower right on the final approach course about 2 miles out up to 1060 MSL ... so, the minimums for the approach were 1360 MSL ... pretty easy math.
I'm sure there's a standard for DH, but I don't know what it is. It is less important because, unlike an MDA, you won't be hanging out there. You get to DH, you either land or miss, whereas on a n-p approach you might be flying at MDA (or a stepdown fix, for that matter) for a mile or two to the MAP.
The 300' obstacle clearance only applies to circling minimums. Additionally a circling MDA will not be less than 350' HAA.
Obstruction clearance on final varies according to the type of approach and other criteria such as: length of the final, distance to the altimeter source, and alignment of the final to the landing runway.
Normally an MDA requires a 250' required obstacle clearance (ROC) predicated on a 7:1 descent gradient. (This is one of the reasons why the "dive and drive" method of flying a non-precision approach is giving way to the "constant angle" technique) The MDA DOES NOT necessarily provide a clear zone all the way from the FAF to the MAP. The straight-in landing MDA will not be less than 250 above TDZE.
The ILS GS normally provides obstacle clearance from 660' at the OM to 110' at DA (200 DH); but if required vis is at or above 1 mile an obstruction could penetrate the GS inside the DH.