Rental Value

Rental value is the rent a property commands on the open market, also called fair market rent. In BRRRR it is the input to the rent step: the finished property's market rent sets its net operating income, whether it covers the new mortgage, and, with a DSCR lender, the loan it qualifies for.

Estimate it from comparable renovated rentals nearby before you buy, not from the listing or the seller. A $200 miss on $2,300 of rent cuts NOI by about $1,870 a year, which on the default deal takes cash flow from positive to negative.

The refinance lender will check it too, through the appraiser's rent schedule, and will qualify on the lower of the lease and the market estimate. A lease signed at market before the refinance is the strongest position: it proves the rent and the property's status as a stabilized rental, which many lenders require before a cash-out.

Further reading: Rental Value on Wikipedia.