Obviously with the 60-feet setback I can barely build anything anymore.Should I hire a surveyor or geotech to mitigate the issue?

If you want to mitigate your risk through research, you will pay with your time.

My husband and I used to think that we liked to be geographically diverse, to mitigate our risks from local area economics.

Beware of these motivated renters, do your due diligence (understand why they have to move, their circumstances, etc.) in order to mitigate your risk.As for having properties in the same area, I'm in favor of this strategy!

My question for this community is: what mitigation strategies do you know of to prevent smell coming into the unit? 

It's those maniacs that buy homes cash via quit claim deed off of craigslist that really get screwed.Make sure your property manager is a licensed real estate brokerage.Google Clayton Morris and/or Morris Invest for a cautionary tale of what not to do when buying turnkey real estateUnderstand you can not eliminate all risk, only mitigate it.

Make sure to get a wind mitigation report.

No major outbreaks and zero deaths.

We plan to hold our property for the long term which mitigates that risk in my mind as it's unlikely we'll be forced to sell during a downturn.

Retail tenants can go BK sometimes fairly suddenly even if the risk is mitigated and proper due diligence is taken.