Due on Sale Discussion/Idea

[Dane Hamilton]

Hey guys, one of my buddies recently introduced me to an interesting deal structure. Here's my example for discussion:

There's a SFR with a seller with a mortgage who's interested in a Subject 2 deal. Let's say the home is worth $450k and the monthly payment is $2500. I do the deal, take ownership, and I start paying the seller's mortgage payment. At this point, I've acquired the property for just a $2500 monthly payment (awesome).

Then, I decide to turn around and sell the property to a cash and/or conventional mortgage buyer for $450k. IF the due on sale clause is not called, then I walk away with $450k in cash, and I'm still obligated to a $2500/month payment. 

Did I just create $450k in cash out of thin air? Is this possible/legal? How can this go wrong? What happens to the note collateral after I sell the property to the new buyer? Am I doomed because of the Due on Sale clause?

Help me out guys, I'm still new to the game. Thanks in advance for your responses!