Although a step in the right direction it is a feel good regulations.The average low in Denver is 17°, which is super convenient because that is one of the temperatures that heat pumps are tested at.At that temperature, an air source cold climate heat pump is taking one unit of electricity and converting it to two units of heat.Your typical gas furnace is 80% efficient.

You obviously have some seasonality, but use the next 30 days as a gauge for demand since I don't think right now would be considered peak season in your area.From some testing that I've done on Airbnb in Portland, there is always a rate that will get you booked with near 100% occupancy.

Jaron is right, don't fully dive right in without testing the water first.

In my opinion, a CPA knowledgeable about the asset test rules is a better resource than an attorney in terms of ongoing compliance.  

Also, take as many practice tests as you can, as often as you can. 

Study study study on deals, it sounds like you may have a deal but yes the 10 years vacant is a huge red flag (buildings in this area for example have iron pipes that collapse when the units go vacant for extended periods and cost tens of thousands just for that, do a sewer scope test as part of your inspection!!!)

The key point is to stress test your numbers in a range (say .5-1% spread). 

I've tested a few apps & none of them are that great & have completely different results, as I'm searching primarily for multi-family properties.

Test it by paying for 2 appraisals -- one with and one without an active contract. 

But that will cover the sniff test  and then you can decide.As others have mentioned unless things have radically changed in Memhpis a 140k house is a pretty good area and good house and should rent for that 1200 number.. or more  not 950.. that's the first problem with your math.