@Amy Webber, @Andrew Emery, @Andrew Johnson, @Bob B., @Christopher Meis, @Cody L., @Dave Charlton, @Kevin Coggins, @Kevin Coleman, @Jack Clough, @James Slaughter, @Jonathan Jewell, @Lesley Resnick, @Miniece Richardson, @Robert Bohigian, @Russell Brazil, @Account Closed, as promised I've returned to this thread to provide an update. The seller agreed to pay for a structural engineer. As it turns out, the garage slab was not poured over the house foundation on the left side of the garage. As a result, the poor compaction of the soils on the left side led to severe settlement of the garage slab. The right side of the slab did not settle because it was built over the house foundation. However, the severe rotation of the garage slab (from the settlement on the left side) caused the horizontal crack along the garage (where it is attached to the foundation on the right side).
The garage slab settlement has not damaged the structure of the house. However, the settlement needs to be repaired and the slab re-leveled (as much as possible). The engineer recommending using structural foam or pressured grout, which is basically injected under the garage slab. I placed calls to 10 different foundation companies in the Atlanta area. Only two of them would provide a ballpark quote over the phone based on the engineer's report without seeing the property in person. One of those two companies straight up refuses to work with structural foam, and the other company strongly recommended against using foam as it's only a temporary fix. Both companies recommended the pressured grout, which may not provide as much lift as foam would, but it is basically a permanent fix guaranteed to prevent any further settling.
The quote from both foundation companies for the pressured grout was basically $4,000. The two quotes were very close. The seller agreed to provide a $4,000 credit to cover this cost. Since FNMA will not allow IPCs in excess of 2% of the purchase price, we went with a $1,700 closing cost credit + a reduction in the purchase price of $2,300. The closing happened today. I'll get the property hooked up with my property manager over the next couple days and then have the repair scheduled shortly thereafter.
Thank you everyone for your help and guidance!