Real Estate deals without money lending or crdit card??

[JJ Parente]

Hi, I was recently watching videos on flipping houses when I came across an idea I hadn't seen before and I was confused on how it worked. Instead of getting a private lender to step in this guy said he makes contracts for homes and simply takes over the sellers existing mortgage. He also says that he puts in clauses so they cannot come after him. How exactly does this work, and is it a good idea? Thanks in advance! heres the link to the video