Single Family Owner Wants To Invest In Duplex Or 4 Unit, Need Advice

Hello, I just bought a single family (my main residence) three years ago. Bought for 250k. Surrounding like properties are selling for 390k. I appraised the house six months ago and it appraised for $330k. I want to buy investment property. How can I do this without pulling too much money out of my main residence now? If this is not possible, I'd like some suggestions on some financing options. I am thinking about obtaining a duplex or four unit property. My friend tells me I need 10% down. Is there any other way around this? What about l/o on investment property? How does that work? Would I be better off with starting with a duplex? Thanks. :-o