Waiting until the 1-year period ends avoids potential loan issues and simplifies things.

I rent to one couple or small family for the full rental period - no less than 2 months and no more than 3 months.

They would get that $500K tax free and the rest of the tax would be deferred in the 1031.A very elegant solution that puts $500K tax free in their hands now. 

-Build a strong network in Detroit of real humans over a period of months, buy a better deal, hold it for 10+ years, weather early storms:  better chance for success.Even on that latter deal though, are you going to cash flow in month 1 or year 1 or even year 5? 

Otherwise, if you are referring to ETF's such as Spiders, or QQQ, the the holding period rules apply.

It wouldn’t even be listed on Airbnb during this period so I wouldn’t get dinged by them for blocking the calendar.

Keep in mind that they can increase that period if they get complains from the community, so make sure you're in good relationship with your neighbors.

When it comes to these types of auctions by the sheriff, is there a waiting period that must be observed before rehabbing/renting the building post winning the bid?

Just remember anyone who has acted as your employee, attorney, accountant, investment banker or broker, or real estate agent or broker within the 2-year period ending on the date of the transfer of the first of the relinquished properties is considered your agent and is disqualified from being your QI.So definitely ask them for recommendations but they cannot act as your QI on the exchange. 

You don't need to know everything to get started; you need a foundation to build on, and the rest will come through experience and then refining your education.You can build a basic understanding of investing in 3-6 months.