Has anybody bought Brian Page's BNB Formula?  

(emphasis added).Unless I'm misunderstanding you, this is a formula for disaster, Perhaps you're suggesting @John Keenan load up his offer with contingencies that will allow him to bail out later when he's finished his homework?

No excel sheets - unless you keep on checking the formulas for accuracy.

If i get to the point I need to replenish because I dipped below that level, I stop taking a monthly check and refill the buffer.I use this spreadsheet to account, it came from BP library but I corrected a lot of the formulas and look up tables and added several lines for income.

I'm sure there isn't an exact formula and it depends on the area and other factors, but if there are rough rules that people follow it would be helpful for me to hear them.Lastly, the cash flow on this property isn't going to be much (after setting aside 5/5/5 for vacancy, repair, and cap expenditures) until I am able to bring the rents up to market rate, so I will be managing this property myself.

Remember that market value isn't determined by calculators or formulas, it's determined by what the highest bidder is willing to pay.A lot of the older BP content & calculators was made by folks who got started in the Midwest about a decade ago, specifically in Colorado.

Here's my wealth formula:  Spend less than you make, and invest the difference in something you understand and control. 

For instance, they determine the formula for calculating bedroom size.  

There is a lot of information here on how to evaluate deals. however knowing the formulas on how to evaluate deals is only part of equation.

They use a "degree day" formula to calculate usage so they knew when we needed a delivery.