Conventional loans are available with 5 - 10% down. If you are in a rural area, you may be able to obtain 100% financing thru a USDA program. If you will be selling the duplex prior to buying, you would be eligible for another FHA loan as well.
It is a good idea to check with an experienced broker in your area as they will have access to many difeerent program. It should be easy to find one that will take an application without you having to pay a fee. Then, if they have a program that is suitable, you can proceed to looking for a home.