Quote from @Jaron Walling: How long have you owned these properties and what are worth today?

None of our renovations would be changing exterior walls.

It's not just about numbers; it's about the families who envision a brighter future within the walls of their new abode.

Maybe there is gold behind the walls? 

The gas light pipe in the walls says 1860 to me, knob and tube replaced that in early 1900’s I suppose .

You can get hefty fines for let's say doing new plumbing work and closing up the walls before the city can inspect, same with electrical. 

If the house floor seems to jump, bounce, or wobble when you walk on it, that floor and maybe the walls, were not likely built correctly.Check EXACTLY where the house is located based on the fire zoned maps. 

A regular partition wall with insulation is not going to cut it for noise sensitive residents.

I’ve gotten multiple quotes for retaining wall and driveway replacement.

Another wall I just hit that I'm navigating is I apparently underestimated Landlord insurance cost, which is biting into my bottom line.Just considerations I'm finding!