As a realtor doing BPOs I am usually guided by past similar sales and current listings, and I usually go by cost per Sq .ft.

Check out my profile and listen to the 3 podcasts I have listed there just to give you a sense of one of many ways to accelerate your growth.

They're probably doing a "Hey John, I know you're listed at 100k but do you think your seller would take 65K?

To give you an example, a seller received an offer next day the house was listed, and accepted it, in 3 days after the seller received a better offer, his attorney gives undoable conditions to the already signed contract, like bringing a closing day earlier.

Since you're posting this in the rent to own forum I'll assume that you plan on listing your rent to own deals on the MLS.

Onslow and others) have unofficial 'good' and 'bad' lists of contractors that they deal with.

Also, if the house is already listed for sale, would there still be realtor commissions to pay if this goes through, or would that hold off until the house is officially sold?

You'd want to be on @William Allen's buyer's list for sure.

I'm about to list my Chicago parking spot for sale.  

I actually need a photographer for a listing.