Get pre-approved first, know your target price and realistic rents, and be honest about whether the market you're shopping can actually cash flow. - Expect a larger down payment. The 5 percent minimum on a conventional 2-4 unit purchase applies when you live in one of the units. A true investment duplex takes more down, so go in knowing your number before you shop. A mortgage professional needs your target price and realistic rents to tell you what actually pencils. - Be honest about the market. In high-cost areas like Southern California, duplexes rarely cash flow, because the purchase price is so high relative to achievable rent. That's exactly why so many small multifamily investors buy out of state, in more affordable and emerging markets with growth potential. Most people who own 50 to 70 rental doors did not build that portfolio in Southern California. - Know where residential ends. A 2-4 unit building is still residential financing. Five units and up is commercial real estate, with entirely different loan structures, down payment requirements, and rate rules. That distinction also explains the scary headlines: the "real estate is crashing" stories are almost always about the commercial space (think short-term adjustable loans on buildings that stopped cash flowing), a different world from the 1-4 unit residential space you'd be buying in. When you're ready to see what a specific duplex does to your numbers, that's what the free Roadmap conversation (about 20 minutes) is for.