Even if your seller replaces the items you mention, you still have many items that will need repair over time.

Literally replaced almost every surface in both units.

I am wondering what kind of flooring is best to replace it?

I am wondering what flooring will be best to replace it?

Assume $7500 to replace. $7500/25 year life span/12 months in a year=$25 per month for the roof if new.

Finally, you can rip out the ceiling and replace it with new drywall, or, if the ceiling is made of plaster, you can remove all the plaster and screw up 3/8 in. drywall on the existing lath.But here’s a common scenario in 100-year-old housing which @JD Martin mentioned in passing : the popcorn ceiling is on the second floor of the house and the floor joist bays in the attic are filled with asbestos-contaminated vermiculite.

Don't replace face to face, voice to voice contact with real live people! 

I’ve had to replace the roof and put in a new HVAC system.

Are you looking to replace all of your income with REI?

Carpet will need to be replaced, wood will be durable, but also, without knowing the rest of the materials in the house, you probably want it to flow into the area you're entering.