It was rust looking because of the fertilizer she used Another said the insulation was too deep in the attic and could start a fire  🤨 My friend is a fire safety inspector   He took a look, said the inspector was completely wrong 

We are doing roof, windows, full electric, all plumbing above the slab, new water heater, installing new central a/c(it had window units), 70% new sheetrock, cabinets, vanities, flooring, insulation, and some framing for rotten wood under the windows, and changing out all doors.

Not counting that insulation needs to be replaced completely because seller didn't cleaned the attic and has rat poop everywhere.

I have never added insulation on my personal residences or flips, beyond my gut level renovations.  

There is a housing inventory problem right now, and shortage of affordable housing, which provides a layer of insulation if there is a major correction/crash.  

Everything on an old house can be upgraded....the hardest thing to do frankly is the insulation in the walls, which needs all the drywall/plaster ripped off to install.

Maintenance and lack of insulation for a property of this age scares me, but these seem to cash flow better.I have come across a duplex that is built in 1955, all brick, but if my numbers are correct, it will only cash flow for about $250 total per month.

They can't see how much work you did behind the walls with framing, quality insulation, updated electrical, super quality craftsmanship on the plumbing.. it matters that you have updated mechanicals and they will quantify it but... what really matters is the quality if your finishing work. 

The less you open, the less you have to replace/repair.When you do open up walls, insulation, electrical and drywall will be the main things to look at.

You would have to calculate based on square footage, then consider variables like insulation, outdoor temperatures, etc.