Need help with possibly my first deal

[Minh Pho]

Here is the situation

ARV is $280,000
A rehabber was going to buy it but ran into money problems.
He has 3 days to close or his broker will be upset with him.
He can get it for $110,000 and wants me to buy it for $120,000
I have a buyer that is ready to go at $135,000

My question is, what purchase contracts and assignment contracts need to be in place to protect everyone involved starting with he broker.

So the chain goes like this. I know double wholesale is usually not advised, but seems like the numbers work.
Broker -> Seller -> Me -> End Buyer

I don't know what kind of contract there is between the broker and the wholesaler. So I don't even know if what he has is assignable. I think he just wants us to come to the table with cash. Is there some sort of contract in that situation?

Thanks in advance.
Minh