Probably none. The Earth's core is hotter than the surface and the surface temperature of the crust basically reflects the average atmospheric temperature.

Up north in the US the average ground temperature is maybe 40F at 10ft down (which is why there are basements up north, to get below the frost line) but here in Texas the average ground temperature is about 70F. At the equator it's probably more like 90-100F.

Given that Venus' atmosphere is so hot it seems likely that the deeper you go the hotter it gets.