You can buy anything from 1-4 units using an FHA loan. There is a limit on purchase price; somewhere around $640,000 if you meet he income guidelines. If I were you and if you can afford it, Id maximize the ROI both financially and educationally by purchasing a fourplex rather than just a duplex. There is also more security in it as you have more tenants paying your mortgage.
The home needs to meet certain habitability points prior to closing like no lead paint, everything in good working order like smoke detectors. Common sense stuff
Ive used an FHA loan 2 times now and ill be looking for my third when the market settles down. You just need to be careful in this market because the payment can quickly add up as taxes, insurance and also PMI is included in your payment. So when the values drop out whether its like '08 or just a small amount, you still need to pay the mortgage. My advice, keep your exit plan of refinancing in mind before signing up for this.