Question about BRRR and Refinancing

[Rob Bianco]

I'm currently rehabbing a single family home and turning it into a duplex. I paid cash for the property and after completion my investment should give me a 30% return each month. I'm debating whether or not to refinance the property after everything is done and tenants are in place... I'm not entirely sure I understand the reasoning behind refinancing when you could instead keep all the cash each month and not have to worry about a mortgage especially if there's a long vacancy, economic downturn, etc... etc...

I'm hoping someone with experience can shed some light on why refinancing would be something I would want to do.