Rental income can be used in various ways really but usually they want you to cash flow $1 after taking out their expense ratio from the gross rent. 

Hi Christopher, I'm a realtor in the area and I thought I'd run some numbers for you just to get a better picture of the risk/reward of a LTR vs STR.Currently netting $250 a month on the LTRIf you rented it as a STR on a nightly basis for $135 with an expected estimated vacancy of 56% (average for the area) that's a gross income of $21,681 less your mortgage $17,400 and less expenses such as water electric and internet of an estimated $4200 puts your annual net at $81.To make the STR profitable for the additional work you'd have to rent it for more than $135 a night and for more nights than the Nashville average of 44% occupancy. 

(I think that's in line with the idea that rent should be no more than 1/3 of their gross income to afford other expenses.)

In any event some lenders will count up to 75% of gross rents as income while recording mortgage, taxes, insurance, HOA fees as "front-end" debt payments.

Eg if you charge 1300 a month for 3 bedroom charge 150 weekly and fill 4 beds (1 room for sober house manager) = $2400 gross. 

For us BP people, we can see the potential in a fresh coat of off-white paint where regular people just see a gross ugly house.  

If you're applying for a Conventional/FHA/VA/ or USDA loan, then they will do a "global cash flow" where they take into account your PITI (Principal + Interest + Taxes + Insurance (hazard and flood) on all properties (second mortgages included), HOA payments, car payments, student loan payments, credit card payments, and installment loan payments in the numerator and your gross income in the denominator.

On a 50 sq roof to have 450 gross. so 22k in two days, they are making much more than 4k. the 20% you mentioned.

So "IF" one argues there "safe" because of Cash-Flow, and that is say 10% of gross revenues, for example $240 per mnth net on a $2,400 rent.....   

The neighborhood has a strong sales history, and I should be able to gross $38k.No school or class will replace the value of getting started and learning your trade.