Capex and tenant issues tend to exceed cash flow and when you decide to exit after a couple of painful years, you are in for another surprise:It is shockingly hard to sell cheap homes! 

Also, any advice for avoiding those unexpected surprises (or at least making them less painful) would be super appreciated.

I paid PMI which feels painful but if you keep your eye on the long term prize it's worth it. 

What pain points or problems have you encountered or seen when evaluating real estate deals?

You can Google it, but in general Judicial=Longer, more painful foreclosure process.  

The time it takes for the draws from tenants and then the ACH transfer to you leaves you getting pain on the 7th or 8th of the month, the $1 ACH transfer fee is an annoyance that has drawn some complaints that are as petty as the fee feels, the new tenant application features are sub-par, and I'm not sure how well it properly informs tenants of the additional charge for credit cards as I got panicked texts about the added fee from a tenant already going through some hardship.

Real estate is not for everyone and is a pain in the a## if you don't really like it.

I lived in Los Angeles, so I get your pain.

Most of the negative feedback on BBB has to do with their lack of responsiveness, which could be a growing pain issue since they are affiliated with at least several large REI groups that I am aware of, so are presumably overwhelmed with new business right now.

Since this house is one I Airbnb part-time and live in part-time it's more painful because I have to experience and see all the issues myself!