Is it a simple subtraction of the your buyer's offer and the purchase price?

Subtract your other assumptions and it still looks like a decent cashflowing property.

It does not account for the fact that you still have mortgage remaining when you sell in year 10, which needs to be subtracted from the cash flow.

They will then take the other 75% of the rents and subtract the PITI mortgage payment of that home.

After subtracting PITI from rents, my gross income is $160.

I normally subtract 10% for every month it's been listed.

you just do the calculators as if you were not living there and then subtract the rent you would be "paying" yourself.

The lien would be subtracted from the sellers bottom line at closing.

So for my understanding a good way to judge it is to take the property and based off of local rents for that area get the average % of rent to value, subtract repairs and there is your comp value.  

I'm looking to purchase a foreclosure as my primary residence as it has a studio apartment over the garage that I should be able to get $1500 a month from while renting my current home for $2000 a month, which would result in a net income of $1185 a month (subtracting the mortgage on my current home).