Can you explain the BRRRR method to a beginner?

Buy a run-down rental below what it will be worth fixed up. Renovate it. Rent it out. Then refinance into a normal mortgage based on the new, higher value. If you bought cheaply enough, the refinance pays back the cash you spent, and you own a rental with little of your own money in it.

A house that needs work sells for $300,000. Fixed up, similar houses sell for $500,000. You buy it mostly with a short-term loan and spend $60,000 on the renovation. About $121,000 of the project is your cash.

You lease it for $4,400 a month. A bank appraises it at $500,000 and lends 75%, $375,000. That pays off the short-term loan and hands you about $94,000. You now own a $500,000 rental with $125,000 of equity, a tenant, and about $28,000 of your money still in it. The $94,000 funds the next house.