It seems like no one ever thinks to get this regular maintenance done. 

It will only take you experiencing this once to make a change for the better next go round.

Do you think the answer to either of these fronts changes if the home is a rehab vs brand new construction?

The tax implications in the future will be this: less depreciation after year one (not by much as transient property is depreciated over 39 years not 27.5) and if you ever sell the property you will have significantly more depreciation to recapture. 

The only time that expense/profit number should significantly change is if 1) They take too long (see A), 2) They do work outside the original scope (see A), 3) the original underwriting made bad assumptions about costs/profits, or 4) some act of god changes your exit.

You just have to remember to put the battery changes on your annual maintenance schedule.

I like the AirBnb concept as well. 

During this time would be a good time to talk with a investor friendly lender (where ever you decide to look into investing) to start talking through the opportunities you have.

I've house hacked twice in Reno, NV and it's changed my life. 

I am a beach bum so El Cajon will definitely be a change for me but I am willing to make the sacrifice.