Deal formula ?

[William M.]

I was watching a video from cash flow diary. He was describing his deal formulas. He said that he takes the gross annual income and multiples it by 2 and that's his all in bid. Did I misunderstand what he's saying? That would mean you never buy a single family home over $30,000. A house I have in VA rents for $1,150. 1,150x12= 13,800 x 2 = 27,600. So with his math I shouldn't have payed more than $28,000. What am I not understanding? Is he only talking about property with multiple units.