as someone how as overseen hundreds of groundwater wells drilled, a good driller is a very rare thing. And you will never make much money drilling wells for the general public. The money comes from O&G field or environmental monitoring. These companies tend to require safety training, certain certificates, etc.
If it is just something you are looking to do for a side job to drill a few residential wells, maybe it could work, but I would think the upkeep for the rig and insurance wouldn't allow for much of a profit
How much of a hassle would it be to get them back up and running?