was originally a farm with a classic outdoor well and pump which wasn't our source of water. Garter snakes would hibernate in that i guess dry well and come out by the dozen every spring, but they headed off into the 40 acres surrounding the house and despite a rubble foundation, we never had snake problems inside.
Maybe they need a dry well as far from the house as possible, and a sprayfoam insulation barrier if the house has a basement.
They knew when they bought it that there were a few snakes about but didn't know how many that meant.
It's going for cheap now and one could have worse neighbors.