Mining i can help with. Houses.. not soo much. Mines usually a castle on a terraformed island.
For mining dig down, but not STRAIGHT down, as eagles stated. instead make a staircase as you dig down. when you start, dig one down, then over then 2 more down, then one over, then three down, thus making a staircase. IF you dont find some massive cave system, strat shaf mining. 50 forward, 25 left or right, the 50 forward then repeat