My notes from the walk through inspection with Tenant show that Tenant admitted to only doing less than minimum maintenance over his 9 years of tenancy: 1. reinstalled mailbox, 2. crawled in attic once, 3. had a breaker installed (wrongly charged landlord $250 by underpaying rent on last month), 4. had small repair done on pool, which was not effective, by his own account.  

As part of the re-installation he said he'd need to level parts of the floor with concrete and I said that was fine.

I deleted the app and could not find it on iTunes to reinstall.

On that house, the same guy took up the floor and then went ape-bleep with screws and screwed down the sub floor and reinstalled the finished floor.

You will need proper fire blocks between units, which depending on what's on the connecting wall (like a custom shower, kitchen cabinets etc.) can be pricey to tear out down to the studs, install the fireblock, and reinstall what was originally there. 

The kicker is though, the gas company requires a permit from the city stating that the gas line has been checked and is safe to reinstall the meter.  

Instead, MLGW came out, alerted code and $6,000 later I have all new gas service lines to my triplex, hot water tanks are in different locations, floor furnaces were reinstalled among a few other things.

Worse case scenario, an entire plank/square can be removed in not-so-obvious places, then reinstalled with the tongues sawn off. 

Remove/reinstall commode $150, prep and install tile $5 SF and if it's on the second floor, add $1 or $1.50 SF for tile backer installation.

Either way, you will probably be liable for removing and reinstalling the system during the reroof.