It depends on how much and what components you change out in your capital improvement program as well as many other factors. Other factors include geographic location, mechanical configuration of the HVAC and hot water, type of roofing, type of electrical wiring, work that has been done previously, etc, etc
If all your plumbing fixtures and fans and appliances are new your maintenance costs will be significantly less than if you replace nothing and run it just as you found it.
The National Apartment Association (NAA) puts out a study every year that you can buy. It is the "Survey of Operating Income and Expenses in Rental Apartment Communities". They track by product type/age/geography/etc. That is ball park numbers you might be able to rely on for a 10,000 foot view.
Jan 17, 2011