I could turn around and sell them for at least double what I paid for them, but my plan is to keep them, even if the economy tanks again.

We have no obligation to purchase the house and can leave after the 12 month period is over, so if we end up hating the house or the housing market unexpectedly tanks we can walk away and get our deposit back, just like any other rental. 

Leach fields are sized on how the soil perc tested and the size of the tank.

The vent on your hot water heater doesn't rise, trapping co gas in the duct instead of leaving out the chimney, Has no drip pan, no expansion tank, yet the heater is almost brand new.

No one has separated plumbing in these older areas, so it is not a huge negative to have a central hot water tank and shared hot water pipes. 

I would like to replace hot water tank or even possibly go tankless.

Hot water tank, gone.

I shudder to think about what I would do with 70 leveraged doors if the market tanks...

However if "Your clients best interest" is letting it tank, then you as an agent need to go into "tank" mode and sink the deal (even at a loss of commission).

When the economy tanks, we'll see some serious changes in the landscape.