I enjoyed reading the tips above. Below is my contribution
Create Standards. Use the same products throughout.
Use one color for all rentals. I use Navajo white on walls, eggshell.
Trim and baths are white semigloss
No ceiling paint, use only primer. It saves you $.
Use the same tile for walls and floors of doing a bath. Only use that tile in your rentals.
10 year sealed smoke and CO detectors. It's life safety! I date them with sharpies. You can buy 10 year batteries, too.
Hardwood Floors. Synteko.
Waterproof vinyl flooring and tile are fine. I don't use carpet
Locks. No batteries. Use SmartKey devices. They will pay for themselves after the first turnover.
Lights. Led, 15 year without changing lightbulbs.
Led photovoltaic exterior sensor lights.
I had bought used kitchens and countertops. It's matter of luck and timing. I've paid$800 for 20k in high end (10 year old) cabinets/ countertops
If keeping toilets, change the guts and buy them a plunger!
Put plastic tile underneath the kitchen sink. It will protect the cabinet.
Provide pedestal sinks in bath, no cabinets. It will not rot.
Have a master key in the property at all times. Put in lockbox. This will save you a trip to give access to contractors and when tenants lock themselves out.
Good luck,
Frank