Questions about "subject to" default and purchase price

[Christopher Abernathy]

The seller called off of bandit signs said he knows what i do and that i need a small profit to make sense, called before i could get out to the property and says another wholesaler came by and they were just way to far off on numbers and so he didnt want to waste my time. i feel like from our first convo he just wants to move because neighbors are to close and ready to relocate. 

3b /2b

1,318sq

in winterville nc

ARV: $150k

Rehab: $10k

Loan Balance: $92k

current mortgage: $509 /mo

Possible rent : $1,100-$1,200/mo

I have not written up this offer yet but i was thinking of offering $5-$10k to walk, and sign a contract to purchase at $140k in 2 years, taking over his existing payment of $509,

Then my next move would be to rent to own at $1,200/mo with a $10-$15k downpayment.

If anyone could let me know what you think of this and also let me know about any small items i may be missing.

its my understanding i just need, purchase agreement, power of attorney for the loan, and release of info sign as well as a CYS (Cover Your A$$) letter like Ron Legrand calls it.

I'm curious who will actually make the payment each month (end buyer/me on contract/original owner)? from which account and how does the current homeowner relieve his stress of the payment not damaging his credit and keeping up with whether the payment is made and made on time? it seems like they would need to still keep an eye on their loan each month and also they may get kinda scared or upset if for some reason payment isn't in promptly when due. I have a property that might work for this method here are the numbers.