I know for certain that my box will have to be either external from the house itself but on the premise or in a basement. 

Call a broker in the area or get access to commercial real estate web sites to get an idea for cap rates in the area. 

Several RE companies have good web sites that have loads of  more specific details.

It's a 4-bedroom, 2-bathroom house that has the potential for a basement conversion into a 1 or 2-bedroom, 1-bathroom unit with an external exit, essentially creating a duplex.

Please don't think I'm trying to be negative or troll-y, but if any developer has an algorithm for this, I would wager that developer would be reluctant to publish such proprietary information on the web so they can have more competition.The Knoxville market, and probably most/all of its sub-markets, have cooled substantially due to affordability and lots of other factors.

I'm seeing high electric bills in our STR properties and was wondering if anyone had tried using a web thermostat to reduce power usage when the unit was vacant. 

Once again this is a 30,000 foot view, and not taking into other external factors.  

Search the bigger pockets web site where Scott Smith wrote an article about it last year.

. * Airbnb On airbnb.com go to Host and select CalendarClick Availability settings in your calendar viewUnder Sync calendars, select Export CalendarCopy and paste the Airbnb calendar link into your iCal applications** VRBO In your reservation calendar, click the Import/Export arrows iconClick Export CalendarCopy the URL and follow the instructions on your external calendar in order to importYou're welcome :)

I tried searching the web and only seem to get sponsored ads for firms.