The source is likely from the bathroom not being properly vented while the shower is on.

House is rented out regularly but also has a 2nd homesite that has a septic installed & perked for 2 Bed.

My properties are all in San Francisco proper which I know like the back of my hand, and I didn’t want to exchange into a random NNN in middle America where I know f*ck all about the area.

I also own properties in landlord-friendly states where there's no rent control, so I don't need to pay someone to leave in order to increase the rent.To address the other points in your post:This is why having a proper purchase and sale agreement is so important.

(They have the deferred maintenance you'd expect after a fixed income senior lived in them for several years, plus smokers, pets)So how do I turn 5 straggling houses into a proper real estate portfolio and well-managed rental business? 

I would make sure your property is properly marketed and that your rents are in line with the comps.

I just recently saw a similar post asking if installing PickleBall courts added to ROI.  

I just installed a whole kitchen of IKEA cabinets, and they are farrrrr superior to the lower and even some of the mid level cabinets offered by Home Depot and Lowes.The downside is you have to assemble then, but they are much sturdier than the other big box store cabinets.

Primarily when downsizing they question your occupancy intent (Claiming primary residence on a fixer upper for favorable LTV terms, with intent to convert to an investment in the short term) but everything can be worked out with proper documentation.

Take ownership of your mistake and learn to do the proper due diligence recommended above😊