Making a blind 30% below listing price offer?

[Megan Elise McIlvaine]

So, I watched a Bigger Pockets video with Chris Heeren where he mentioned submitting a 30% below listing price offer with a walk-through contingency in it with the hopes that the seller would then counter offer and give you a two to three day period to check out the house. He also said that he doesn't submit this offer if it doesn't follow the "teen percent role" but it wasn't clear which number that was and also if it is the Cash on Cash ROI then how would he be able to estimate the cost of renovations to find that teen number if he hasn't seen the house? Thank you all again!