I was informed by KCMO Health Department that landlords are supposed to be paying an annual fee to them and they conduct inspections of rental units in the city?

Get pictures of every room, the electrical breaker box, water heater, furnace, each side of the house, the roof, the basement if there is one, inside and outside of the garage if there is one etc.If the seller doesn’t want you to come do a walk-through and take pictures due to concerns over COVID-19, then have the seller take pictures and send them to you.

If there is "still contamination" at any level, I would be concerned about that and pass on the deal no matter what.

One concern that I have is that I need to be able to sustain this during a downturn.

Most seller's in a sub-to don't understand the risk they are taking and most lenders have concerns over the overall portfolio quality ratings which has an impact on their cost of funds.

But my biggest concern is that such a large expense for such a short time would not add as much value as what I'm looking for.

Both of these are legitimate concerns.

Please see my earlier response to address your concerns.

We plan to rent out the main house and ADU in the future but also concerned on the return if/when we do sell. 

I think governments have a role to play in trying to tackle affordable housing concerns, but even I think the reclassification bill will crush the little guy, or at a minimum needs revising.