In my model I tied the rent to the purchase price (Rent = .008* Purchase Price) so i couldn't really test that variable much without some sort of data table. 

The statute makes clear, however, that while a married taxpayer includes the hours of his or her spouse in determining whether the taxpayer materially participates in a real property trade or business, the taxpayer must pass the two quantitative tests of Sec. 469(c)(7)(B) using only his or her own hours.35"

While this may exempt it from being classified as a rental activity, active participation remains a requirement, necessitating compliance with three tests: spending 500 hours on the property, dedicating at least 100 hours (and more than any other participant), and performing all the necessary work needed.Additionally, long-term viability and consideration of depreciation recapture are important concerns.

Material participation tests are the rules the IRS uses to determine if you worked on your short term rental business on a regular basis during the year. 

Cash flow, we don't buy any properties less than 50% of what they're worth, all our properties we own make positive cash flow in a modest way and these tow items are deal breakers if they don't pass that's test for us on str.

Be careful, that 100 hour test includes language along the lines of "100 hours AND more then anyone else".

Bring a marble to test the floors.

I collected MTR comps and ran the numbers, and found that I might get an extra 15%-20% from a MTR, but I'm not sure if the vacancy rate I plugged in was reasonable (I'm in a mid-size city and my properties are close to Universities, hospitals, and other things that attract MTR tenants, so hopefully I'd have low vacancy...but I like to play it safe with my numbers, so I try to allow for a good bit of vacancy)... ...plus, all the comps I collected were just listings this month, and I don't know how much they're affected by seasonality, so my rent data might not be super accurate... ...maybe I'll give it a test run with one unit that's opening up in May, and see how it goes...

They just can't imagine that sometimes things just don't go your way - that wasn't on the test!

With FHA loans, there is a self sufficiency test.