You're right to understand that the home won't value, but so long as it performs adequately now (assuming you have vacancy and repairs), and it is in good shape, then I'd lean on the cashflow and the potential options with the land underneath it.

Simply put, the poured concrete is added underneath the stone to get the extra height.

You're also probably going to want a geotech engineer to look at your soil to determine if any remediation will be needed to build a new foundation...Is 600 sq. ft. the footprint of the building or total sq. ft. that you can add.

This is more than two months of profit per SFR, and makes my cashflow take a large hit.Is there a way to have a "main LLC", and multiple "sub LLCs" underneath it, where I would only pay the LLC fee of $800 on the main LLC?

The main thing with any kind of pavement treatment is to keep surface moisture from the soil beneath.If the paving is in good shape (i.e. no alligatoring or potholes) and looks like it's graded OK (no standing water after heavy rain), a seal coat can add life to the property.   

When trying to fix the septic system, I was halted by Baltimore County due to bad soil drainage.

Underneath both of my units is a total of six bays worth of garage space.

You only filled with clean soil though right?

I understand that we had a mutual agreement to put blinds up in lieu of rent decrease to cover those costs early on in your lease, but it seems as though those blinds didn't stay with the property.We had to hire a cleaner to clean: the refrigerator (inside, on top of, and underneath), the inside of the oven, shelves in the kitchen cabinets, tile in the shower still had hairs on them, windows, and all of the hardwoods needed mopped.

Can't they slide a beam underneath and then lift it up to support the floor?