Great question. I know of no grants for move-up home buyers, but there is a soft-second mortgage (an interest and monthly payment-free loan to help pay closing costs and down payment) available depending on where you're looking to buy.
As you'll see from the link, there are limits on the purchase location, price and the household income to participate in this program. One (of many) good things to keep in mind, however, is that this program applies to almost all of the counties in Metro Atlanta.
Another option might be the $100-down program available on HUD-owned Homes.
Yet another option might be to take advantage of the various Neighborhood Stabilization Program properties available throughout Metro Atlanta. These are properties that have been bought and restored by some of the various metro municipalities before returning them to the market and some offer up to $25K in soft second mortgages that are forgiven over pre-set periods of time.
Again, these are not true grants, but may provide the solution you're seeking through your question. If you are not working with an agent, I'd welcome the opportunity to speak in greater detail with you about the right program for you
REALTORÂ® Keller Williams Realty Atlanta Partners