In the DFW area, flipping refers to putting a house under contract, then assigning that contract to an investor who will pay you a "finder's fee". It is that term, "finder's fee" where there has been some debate whether or not it is legal. For the most part, the term now used is "assignment fee" and there are no problems with that.
Further, there has been some debate as to whether or not assigning a contract is legal. As long as when you put a house under contract you put "Your Name or as assigns" as the buyer, you are fine. Thin when it come time to Flip it, a simple one or two page document is all you need.
Dozer