What are good and affordable options for interior doors for rental apartments? 

I own a rental that I had to do some interior work on; patch holes in the drywall, painted the inside, new roof, re-did the outside of the chimney, new carpet in three rooms, and bought a fridge and stove for it, among other smaller things. 2.

New paint on exterior and interior, new baseboards, light fixtures, cabinets, stainless steel appliances, new tile surrounds in both showers/tubs as well as new tile accent wall on fireplace in living room.

Painted interior.

The house definitely needs some upgrades on the interior and some cosmetic fixes too.

Just buying 5 gallon bucks of paint for full interior paint will cost you a few thousand.  

Although I believe you’d need to keep an interior door access to the upstairs as the house is zoned single family.  

Most of my projects are just opening, adding or rearranging a couple interior walls, and if we're not doing anything structural I shy away from permitting altogether.

Part of the cost of doing business.Now if your city's ordinances require rentals to have gold-plated toilets, motion-activated interior lighting, and new interior paint every 2 years, then yeah, I could see how that's unreasonable.

This is super important long-term to maintain the integrity of the interior.