Intuitively, probably just do a price reduction because once you open up walls, who knows what else you might find.

I only allow a few small nails per wall.

Inspections are good start, but they don't check anything that the inspector cannot see so once you start opening walls, you might be in a big surprised.

You'll need to figure out how to wire it (it's not that tricky, a lot of devices have a 12v power supply) or pick a different model that can plug into a wall but has similar specs. 

When you choose a living situation with other people above, below or beside you that share walls, especially an older building, you should not be surprised that you may hear babies cry, toilets flush, alarm clocks, phone calls, etc.

I will say though, if you take a look objectively you might easily find a way to adjust the floor plan with just adding a wall or door.

With me as your agent you get to meet me at the house and I bring trash bags and we clean together all the stuff you don't want covered up in the walls.

You had better be on call 24/7 as your tenants will likely rarely sleep and will be digging holes in the walls looking for FBI cameras and copper wire to sell!     

Wall street is taking a commission on every transaction.

Some Wall Street forecasters claim 100K to 300K with about an average of 150k by end of 2021.