There are some great answers here, but I will toss my 2 cents in anyway!
I own several duplexes in the 55408 area. Depending on the quality of renovation/updating, unit sizes, layout, amenities, and most importantly location ( near 35W or Calhoun) you can expect to get between $900-$1300 for a 2 bedroom 1 bath unit. in unit laundry, garage, etc will add more.
If you would like help looking for investment properties, I specialize in the area.
Keller Williams Integrity Lakes