That is a tough question. The Unincorporated areas of DeKalb and Fulton are the areas that are not within city limits. It would be difficult to give you specific zip codes as many zip codes will be in both Unincorporated and within city limits. You may want to look at specific areas within the county and check to see if they are within city limits. Sometimes taxes are not necessarily lower in Unincorporated areas...if within the city limits your county taxes are slightly lower. It may all come out in the wash depending on where you are looking.
I would be happy to help you in your search and you can contact me anytime for advice and/or listings!! I can research the areas in you target range and can sort out which are in Unincorporated areas.
Lisa Allen, REALTOR
Prudential Georgia Realty