The condo concept may help characterize this as rental income, but I am not sure.  

Would you characterize it as a good area for investing?  

As for property taxes being "high" or "low," in general the characterizations of them I think is made too superficially. 

And this factors in zero future appreciation on the property, zero rent appreciation, and doesn't take into account the tremendous tax shield from aggressive depreciation.So I'd characterize 30% as a slam dunk, 40% as very reasonable, and 50% as doable with intensified effort.

It is generally not beneficial to re-characterize passive income as self employment income simply for the purposes of establishing a Solo 401k plan.A company does not have to be profitable to establish a 401k plan, but does have to generate the right kind of income.  

The IRS will re-characterize your income based upon a typical salary for the work completed.You do not receive the right to receive the cash based upon the minutes, you receive it based upon the fact you have either contributed or paid tax on the income.Even if they corp said no distributions this year, then the owners are paying tax on their share of income despite never receiving a dime.

Can I re-characterize back to non-Roth, then roll over, then re-convert to Roth?

For Self Employment tax purposes Revenue Ruling 58-112 characterizes a trade or business activity as one that is regular, frequent and continuous.

Your characterization of Durham is not complete or accurate.

That is, ultimately we are not the final decision makers and at best we would be characterized as "intermediaries".