Lawman once bubbled...
Mike I don't know how anybody makes a living in the dive business. Especially inland from oceans and in the north.
Maybe a full service [water, equiptment, training, and repair] will generate enough cash for a few people, but not very many.
If I had a quarry big enough to dive I'd make it available for students [as I said earlier] stock it with fish and let people fish the remainder of the time and stick a couple of condos up. Don't fill it with junk, landscape the hell out of it and hope to sell out in a few years.
As Mike said, the owner of Gilboa quarry in OH is doing pretty well. However, he has done a boat load of work....he has put in some seriously long hours, and though he might seem strange and loopy from time to time...alright, most of the time....he is very passionate about the sport and how the divers treat his quarry.
On a given weekend this past spring (may sometime when I was doing my DM cert.) I was working with a group of advanced students. Some came up the night before, and others came up the following day. By doing some simple math with the braclets the owner requires people to wear, we figured that there were at least 200 divers on SAT, and 300 on SUN. That was just the students with an OW cert....the owner gives out different braclets with different numbers for advanced divers. that is a minimum of 5000 for just diving, not counting the number of campers etc.
Long story short, a land-locked quarry can do well, but it is a lot of work