@Thomas Weidner They used to have a formula that if your bid was below their minimum acceptable offer, but higher than a certain threshold, they would counter with their lowest number.

Your formula looks good to me.

Sorry I don't have the time to dig into your numbers but are you plugging into the formula the capital cost of your investment before refi? 

I agree that there's no hard number or specific formula.

I tried to google the best formula to use and came up with NOI divided by total cash initially invested. 

Don't get too caught up in the over analysis trap, it is too easy to do that, there is a formula for everything these days.

When the BP is due, if you have to pay all cash, then you go whatever that pmt is in the hole as a negative cost taking subtracting it for the month it is due from the normal CF formula. 

The most important figure in any purchase & rehab formula is the PURCHASE PRICE. 3.

How can I understand that complex formula??

Here is what I was looking at for the breakdown.Purchase price - 153,000.00 Financing - 122,400.00 at 4.5% for 30 years = 620.00 per month20% Down payment (HELOC) - 30,600.00 at 5% for 10 years = 325.00 per monthRent (Quick look) - 1,200.00 per monthTaxes - (On the website it says 630.00 but on the county website it has a formula with [Tax assessment value x Assessment rate (currently 7.96%) x Mill levy (last year was .088) which turns out to be 153,000 x .0796 x .088 = 1071.73 per year.] 1071.73 / 12 months = 89.31Insurance - (Quick Google search for average) 106.00 per monthVacancy Allowance - (Reading BP says factor 5%-15% so I am going with 10%) 120.00 per monthRepair Allowance - (Reading BP says factor 5%-15% so I am going with 10%) 120.00 per month Capital Expenditures - (Reading BP says factor 5%-15% so I am going with 10%) 120.00 per monthProperty Management - (Usually around 8%-12% so I am going with 10%) 120.00 per monthIn this I am assuming that the tenant pays all utilities and yard maintenance so that isn't factored in.So.... 89.31+106.00+120.00+120.00+120.00+120.00= 675.31 Total So all that added up is....620.00+325.00+675.31= 1620.31 per month420.31 over the 1200.00 rent I know the deal won't work on this one I am just looking at my math to make sure I am factoring everything and just trying to start practicing.