Sorry I cannot add more as there are no formulas for deciding on this risk and values.

I believe it is normal for those who DO apply the "70% Rule" to subtract the Repair costs from the ARV BEFORE taking 30% off (not AFTER), hence, by using your formula you might find it much harder to find an agreeable Seller, than for those who use the "normal" formula ie. why would a Seller sell to you for $107k when they might already have had an offer of $119k from another BP Investor - ostensibly using the same 70% "Rule"?

I know formulas and deal analysis, just need the goods 😁 Any advice would be appreciated as I would like to close another deal before the end of summer, and 5 by the end of the year. 

what is the formula to see if the numbers work? 

I understand the mathematical formula.

For example, I want to flip, so when we bought our house it was a foreclosure, then I used the flip formula to put in an offer price(ARV X .70 = amount - rehab cost = offer price) however the offer price had to fit the amount we were pre-approved for.

It can be a slow, tedious process or it may go fairly quickly, depending on the facts and circumstances.The process and procedure may vary state-to-state, however the basics are that you make an offer and if accepted by the seller (guardian of the minor's estate) certain criteria must typically be met regarding price relating to court referee (appraiser) value and down payment.Your offer may not be the final one, as it may be possible for other to show up at the confirmation hearing and bid up the sale, however in many jurisdictions there is a minimum overbid formula that prevents other buyers from offering the "penny over" nonsense.Most of the time these sales are formalized and either listed through independent or contract broker/agents or the county public admin or guardian.If you're new to real estate, you may find the process frustrating however there are deals to be found.

Is there a formula or rule of thumb on what I should keep in the bank for maintenance/repairs etc so that I may take cash out each month after bills are paid.thanks in advance

Isn't there a formula for taxes in the county?

Flip2freedom episode 77[http://www.flip2freedom.com/a-3-step-formula-to-a-successful-balanced-and-insanely-profitable-2012/] - podcast - LISTEN TO THIS TODAY!