Scott Trench's "Set for Life" inspired my current situation.   

@Colby Mulry this isn't that complicated of a situation. 

How should I handle this situation, while wanting to continue working with this potential future buyer?

Business wise quickbooks or any number of others are probably better for the situation you describe quicken would work fine. 

Don't stress, multi-family can be a difficult market for newcomers.

With full-time jobs and three little ones in school and involved in extra-curricular activities, adding any more stress to our current schedule would spell disaster.

Here’s the deal:Purchase price - $900,000Down Payment- $500,000Balanced financed by owner $400,000Terms 3 years interest only @ 6.5%Earnest Money $10,000Due Diligence 45 daysClosing on or before October 23, 2018My situation: NO capital to invest, bad credit.

Also, what if I write a letter to the bank that has it about my situation?

I think you'd have to evaluate your own situation and make that determination. 

Maybe you could send some scary demand letter from a lawyer to hopefully deter them from filing suit against you for the unpaid charges but it is not a great situation especially since you are out of state.