Linking my bank account has been the biggest frustration.

Without the high leverage you reduce the top source of return in CA RE which is achieve via the appreciation on a high leverage property.  

My intent was to move within a year and rent it out, but we have been having unforeseen expensive issues that I am looking to get advice on.1) HVAC: Our biggest issue.

@Tannia CastroRecommend exploring as many sources as possible to get referrals AND cross-reference them to get as much accurate information as possible.Check out NARPM.com, BP’s Property Manager Finder (BiggerPockets: The Real Estate Investing Social Network), etc.Also, encourage you to learn from the mistakes of others - by reading posts here on BiggerPockets about owners not having their expectations met by their current Property Management Company.

But in my opinion, the biggest issue I see with folks jumping into their first "big" multifamily deal is the quality of the pro forma. 

I’d love to hear from fellow self-managing landlords about the biggest lessons you’ve learned along the way—whether it’s handling difficult move outs, maintenance strategies, or unique ways to streamline day-to-day operations.

At other buildings we switched heat source away from oil heat, too expensive. 

Other sources may get you leads but more don't pan out in my experience.   

There are some public sources (www.city-data.com) that can provide good baseline information.

The good thing about CA, is once you do source a deal, you are pretty much set.