For example the faucets, bathroom hardware, tub/shower hardware, doorknobs, etc?  

I took a sales job with at a hardware distribution company based out of Morristown, TN at the start of 2020 and relocated to Cookeville shortly after to work my sales territory.As I start, I’ve recognized I need to get a feel for this process, particularly in finding leads and making connections!

Band-aid's gotta get ripped off at some point, and the sooner you do it, the better it'll be for your confidence, your wallet, and your lendability. 

Reach in you wallet and get a HVAC or Electrician out there to give each unit full control of the heat and AC on their floor.

For example, if you didn't have separate accounts, when tax prep times along and you look at your credit card statements, how do you figure out if that Home Depot charge was for perhaps some new door hardware for the rental or just something for your own residence? 

He was able to just reseat the toilet when he was done with the flooring - used the same hardware.  

If you had a laundromat, hardware or convenience store, I'd say jump on it.

I'd check Storage Rebellion, you're going to need to invest a bit into technology and compatible hardware.

Typically a $200 hardware investment and $25/mo monitoring fee.

This is how I renovated a duplex in 2020 with only $6,000 (entire 2800sqft interior painting, refinished/re-faced two kitchens and replaced all appliances in each with used/like-new appliances, new sinks, new tile backsplashes, new hardware, new sinks/faucet, 25% flooring replaced, and one bathroom (everything but the shower which was fine as-is).