This is how I personally work out deals in my head so I can analyze them quickly, but make sure you use a more practical formula noted below.Run rental comps for the specific 0.25 mile radius and subtract estimated CapEx (1% of property value/year), vacancy (5-10% of rent), insurance, property taxes, and any other costs that will realistically affect your cash flow. 

Especially after I subtracted it out of their security deposit.  

You can either try to add up the equity raised with the loan and subtract cost of property to see what the delta is. 

You take a ballpark number for anything bad and subtract it and you take a ballpark number for something positive and add it.

Do a market analysis on rent online to get an idea on what it will rent for, subtract your mortgage payment, taxes and insurance, and leave some aside for repair, etc.

American Modern (Annual Cost: $677); Actual Cash value is market value minus land value; I took my purchase price of $113,000 subtracted the land value of $14,600 and came up with $98,400. $1,000 deductible; mold/remediaton - $5,000; personal liability $300,000; loss of rent - up to $9800. 

You pay taxes on NET sale price (subtract any commissions, advertising, closing costs.

Then, you would calculate your cashflow from a prospective tenant by taking the annual rents and subtracting the annual cash outflows (mortgage, insurance, property taxes, expected maintenance and vacancy). 

Subtract from that any expenses (taxes, insurance, avg repairs/maintenance, utilities if you think you'll pay for them, property management if you will pay a manager, a deduction for vacancy).

Airbnb adds on taxes and subtracts host fee of 3%.