There is no harm in trying the short term rental market especially as soft as long term Mpls is at the moment. 

We still put a covenant in the deed to restrict negatives that may harm neighbors land value.Also, our area requires 1.5 acres minimum for sewer and thus minimum lot size in your area for septic (if no sewer available) can be found out by calling zoning office or a friendly developer may be able to help.   

There is no harm in starting to speak with private/HMLs now.

I had met the sellers and knew this would not only be unlikely to help, but would likely harm their chances - I live here, I buy and sell her, and I know this market and the people.

You might want to read our series about “How to Screen a PMC Better than a Tenant”, since selecting the wrong PMC is usually more harmful than selecting a bad tenant: https://www.biggerpockets.com/member-blogs/3094/91877-how-to-screen-a-pmc-better-than-a-tenant-part-1-services-and-processes

In the wrong hands used at the wrong time they could do more harm than good.I am curious what other investors' experiences have been with using these lines.

In December, when the median price reached $600,000, housing experts credited the surge to people whose earnings remained largely untouched by the crisis as shuttered work places left them craving more space.

I'm basically trying to figure out how harmful breaking that rule can be.

If inflation gets worse, I could see places like Portland instituting new laws that harm your ability to make a decent return.

We don’t know any PMCs to recommend in the area mentioned, but since selecting the wrong PMC is usually more harmful than selecting a bad tenant, you might want to read our series about “How to Screen a PMC Better than a Tenant”:https://www.biggerpockets.com/member-blogs/3094/91877-how-to-screen-a-pmc-better-than-a-tenant-part-1-services-and-processesWe recommend you get management contracts from several PMCs and compare the services they cover and, more importantly, what they each DO NOT cover.