Is there a standard letter that I need to send tenants a month before the end of their lease to remind them to move out by the end of the term?

Quote from @Donna Brake: Start the eviction process on the earliest date allowed by the law and your lease.

You just described a rent by the room which would not classify a duplex as a commercial property.

By starting with an ADU or guest suite you have very little risk and can provide excellent service to your guest.

There are many online marketplaces, including BP, where you can post your properties.Aside from selling by owner off the MLS, which offers the greatest flexibility to make a "deal" with an investor, generally it might be best to work with a seasoned investor friendly seller's agent that can guide you through the process and potentially find an investor.

Hello,I am currently in the process of closing on a duplex near Lima, Ohio that I will be house-hacking by living in one of the units for a couple of years.

(No, keep it as it is.)Get this amendment signed by all parties2.

I have looked through the Offering Circular and it states (contradictory to what they state on the website) that the notes "are not secured by any collateral and are not guaranteed...[]". 

I know city of Las Vegas requires host occupancy but areas close by to consider to bypass some of the city restrictions?  

The process is the same that is used on commercial properties but it is advisable to have it completed by a commercial roofing company rather than a general roofer like Everseal.