Enlarged bedroom #1, replaced all flooring, install new HVAC system (install central rather than use window units), replace dilapidated siding, install fencing and exterior curb appeal.

Fixing things that break aka maintenance and also replacing things that are at end of life like a roof replacement also called cap ex (capital expenditures).

I just walked a property where the owner wanted what they bought it for two years ago so I knew it was going to need some work... well, after the walkthrough, it was deemed a complete rehab down to studs including floor joist repair, crawlspace remediation, HVAC replace, etc.

When the reserves are needed, they are transferred back to the Operating Bank Account so that the expense may be paid out of the Operating Bank Account.The Reserve Bank Account includes sub accounts set up in your accounting system for the following reserves: Property tax reserve (fund this account monthly with 1/12 of the annual cost property tax expense)Insurance reserve (fund this account monthly with 1/12 of the annual cost of insurance)Replacement reserve (fund this account monthly in an amount to set aside sufficient funds to cover the rental property's anticipated [inevitable] future capital improvement expenses). 

ie, replacing a damaged bathtub?

A third analysis is replacement cost.

It's several thousand up front and usually shouldn't replace drinking water, but can save a lot of money in the long run.

Find out what it costs to replace it with a similar material and bill them for it.

For example with an investment based Realtor, property manager, and contractor you should be able to seamlessly invest in property, and you get the added value of making sure that your product is still holding to a quality standard along with being able to see your property and replace team members more easily as well if need be.  

We are rehabbers because we remediate knob and tube, we fix rusted sewage lines, we replace a lot of roofs and add insulation in the attics.