To BRRRR, you'd start by either using your own funds to buy and/or rehab the property, place a tenant, then refinance into a long-term loan. If you need financing to buy/rehab, you'd be using a fix and flip loan, which is a bridge loan. These are short term (12 months is common) with a balloon, so you'd want to refinance before that 12 months is up. For the refi, DSCR loans are super popular. These are 30-40 year loans. You don't need to provide income or employment history and DTI is irrelevant, but your credit and whether the property services the debt will be factors. You'll want the rents (or market rents) to meet or exceed the monthly principal, interest, taxes, insurance and HOA if applicable. LTV is typically a max of 75-80%.
if the property you buy already has a tenant or isn't in need of any rehab, you could jump straight into the DSCR or even use a conventional investment loan if you can qualify with employment, income, DTI, etc.