Refinancing an already paid off house.

[Abigail J Steinert]

I was telling my friend about my plans of flipping houses and eventually moving towards BRRRR and working up a portfolio to retire on. He suggested that I buy a house cheap, flip it, then refinance it with the bank even though it would be already paid off.

Why would I want to refinance after I have it paid off or mostly paid off? It's not the first time I've heard this advice but I'm confused.