What is the formula for calculating monthly cash flow to ensure that a potential buyer is getting a good deal for a buy and hold property?

[Lisa G.]

Hi Bigger Pockets Community,

I am a new investor and I have been working on coming up with a figure to present to a seller who is trying to sell their condo. I am wholesaling this deal. The seller gave me their desired asking price but it is higher than the figure I received when I used the formula 70% of ARV minus repairs (no repairs have been given to me from seller) minus my fee. The potential buyer has a set monthly amount they need to receive in order for the deal to be a good one. Knowing this information, what is the formula that I use for a buy and hold property that is being used by an investor as a cash flow deal if I know the desired monthly cash flow amount?Also, how is this formula affected by an existing mortgage?I want to make sure that the figure I come up with is hitting the target cash flow amount desired by the buyer before I present it to the seller.