If an owner with equity files for bankruptcy (BK), can exempt their equity from the BK estate and gets a discharge of the mortgage debt, how (if at all) does that impact the ability to make a deal on the property before it goes to a sheriff's auction?

I understand the discharged homeowner is living in the house for free until there is a sheriff's sale and ejectment, and may not have incentive to make a deal until just days before the sale is inevitable.  How would a deal with the homeowner work in this case?  If you can negotiate a sale that covers the underlying (but now discharged) debt, could that be all there is to it?  

Is there anything about the past bankruptcy that complicates or prevents the sale from moving forward if we agree to an amount that covers the bank's foreclosure judgment. 

Thanks in advance for your replies.