Contracts creating a lease of not more than 1 year may be made orally in Georgia. [44-7-2] The oral lease may include a requirement that T pay a security deposit, which includes damage deposits, advance rent deposits, & pet deposits. It does not include 'earnest money' which is not to be returned to T under the terms of the rental agreement. [44-7-30] (Advnce money is presumed to be a security deposit unless otherwise agreed.) In order to retain any of the deposit, L must have deposited the money in an escrow account separate from L's other funds.
Thus, if T gave you the money with the agreement that they were going to rent the place for 1 year or less (or you gave T the keys), you had a valid oral lease & may retain the security deposit to cover your damages. However, if you & T agreed that the deposit would be returned if T decided not to take the place, it was earnest money & you have to return it. (If T had the option of not taking the place, no L/T relationship was created in the first place.) Assuming there was a tenancy & you deposited the $$ in a separate account, you have 30 days from the termination of tenancy (when T backed out) to return the money or send T a list of charges made against the deposit & refund of any remaining money. Apply the facts of your case to those rules & take the appropriate action.
If you didn't deposit the $ in a separate account, you can still keep the money, but you'll be liable for willfully & wrongfully keeping the money if T sues & raises this requirement. Proceed at your own risk.
Note, if a lease was formed, you can charge T rent until you re-rent the place OR until you moved back in (renting it to yourself). You can also charge T for your expenses trying to re-rent.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.