My husband is a builder in Catersville. He has built addlitional garages on our homes for homeowners or clients ranging in price from $18,000 for a simi attached single garage totally finished to two car detached with attached breezeway from $25,000 to $35,000 totally finished interiors with stair cases to the attic area vs. pulldown stairs. Same exterior finishes as you have mentioned. A few of these homes have come back to me to list over the last few years and we have re-copped all the value. We do think that $50k is high for a 2 car garage. You might ask you contractor to show you a breakdown on his cost and fee. Hope this helps.
Without this information I cannot give you a value, but surely it will not add up to the amount you pay for it, maybe 60-70 percent of the cost to build will be the eventually add on value.
Prudential Georgia Realty
Let us know if you have any other questions.
Adding smart appliances, and all of the right systems will translate well for many buyers at resale, even if they plan to use the space differently.