My family and I have recently been looking at a house to move to, and love everything about it, but we did happen upon three sinkholes. Two of them were about the size of a basketball, and the other was larger, about 4 feet diameter. These holes were outside of the fencing, so horses wouldnt get into them, but should I be concerned about the ground? The owners said they are for sure sinkholes because they are continually filling them.