I understand the process in which double closings and assignments occur, but I'm more struggling with the concept of where the numbers fit in. For a wholesaler, I would simply try to get a good deal on a distressed property and do so with the help of hard money/private lenders (a 70%-80% + 20%-30% ratio), then sell that contract or property to another buyer with an included finders fee i.e a contract for 50,000 plus an added 10,000. 

This would mean that from the 10,000, I would use a percentage of that to pay off the interest that came from the loan is this correct?

I am also unsure of how that works in a double closing. 

If someone could also explain that, I would greatly appreciate it.