The felt alone is $20/ 4 Squares, Cheap shinges will start at $55/square, drip edge $1/ LF, Flashing, sealant, nails, nail caps,  Labor will start at least $75/square if you buy the material.  

We have tried multiple different things short of digging up the front yard but the water flow is strong enough to knock and sealants out of the way. 

Make sure you flash properly the roof to the wall and not just sealant. 

I think you over thinking this in general and not worth it.A  non-curing butyl sealant. 

They have mostly been sealed with a caulk or other form of sealant.

GOOD sealant goes a long way.

As far as I know he didn't test the water heater with it actually ignited.I ordered an OEM ignition system for the hot water heater, and in the meantime put some gasket sealant on the plug, and hooked it back up.Well, 4 days later I get a call from the tenant saying the entire house smelled like gas again.

It's DryLocked and we are thinking of painting it and then finishing it with one of those high gloss sealants.

It's DryLocked and we are thinking of painting it and then finishing it with one of those high gloss sealants.

Pressure washing after spraying concrete cleaning solution will yield much better results and longevity otherwise you will see patches of paint peeling off no matter how expensive or good quality paint and sealant you use.