Thanks in advance.If you have a purchase and sale agreement that's duly executed, I think you could sue for specific performance to complete the transaction. 

If her name is not on the property, can I proceed with the transaction with the ex-husband?

@Nickolay S. you've gotten some good advice above, @Will Barnard is right that banks may frown upon it as an arm's length transaction.

You can buy sub2 as well.All that said, credit is a small part of the transaction, your education, experience, knowledge, team, and abilities all will factor in.

I want to know at what time does the public records gets updated on sites like Zillow, Redfin when the property sale transaction completes ?

All title companies know what a double close is.....the problem is if you’re trying to use the end buyers money to also close the A to B transaction.....here, that is not doable. 

VersusCons:5 separate closings, so 5 title searches, 5 closing Attonery fees, 5 negotiations, possibly 5 different sellers to deal with, 5 locations unless you buy a row of homes which is normally unlikely, possibly multiple PM’s due to location or skill set of PM, 5 insurance premiums.  5 transactions to sell it as well. 

You'll pay transaction costs to do so no matter how you buy (closing costs, holding costs during rehab, etc.)  

You don't want to allow the seller to control the paperwork flow of the transaction.

You have seller finance for transaction purpose, but will have to pick up the income on the cash you have not received.