If it's gas, you could remove it and replace with a gas fireplace, assuming the supplemental heat is required, Just a thought. 

Additionally you can have grandfathered items on old buildings that once they break even if they could be repaired the code says they have to be replaced and brought up to new standards.I know some investors that invest in student rentals.

Last year, I had to replace most of the roof (flat roof) and the ceiling as water had been trickling in over the last 5 years since it was built. 

I'd replace the kitchen counters with granite, but I know that might be out of budget. 

Have a small loft to bedroom remodel which requires some electrical work and window replacement on a third floor.

You can gain some of that experience through education and mentorship, but there is no replacement for running a park yourself. 

A $3,000 A/C system replacement would generally be a restoration relating to the HVAC subsystem of the building and thus capitalized, not expensed. 

Seriously, it’s going to take twice as long and cost twice as much.(5) If the house is 50+ years old and you’re going to hold for long term and not flip, budget to replace the old Cast iron plumbing ( I found roots growing into my sewer line after closing, A very costly unexpected expense). (6) Finally, stay Positive and remember the whole point of the first deal is just to get through it!

I had to paint, replace floor, add a kitchen countertop and cupboards...Do all these qualify as bonus depreciation or do I need to put them under standard?

Offer them something in return (e.g. if you provide appliances and those are old - try to replace the stove or dishwasher), so it seems like a softer blow to the tenant.