Tenant At Will - eviction?

[Ari Newman]

I'm under contract to purchase a SFR in Atlanta. The current tenant is owners daughter and has been living in home for 12+ yrs not paying rent. It appears there was never a lease agreement but a verbal of $200 / month. When I take posession, I know that in GA I need to give 60 days notice to terminate. However, GA law says I have the right to collect fair and reasonable rent and that if tenant defaults on payments I can file for dispossession immediately. If they dont agree to sign an Estoppel agreement stating the terms of original rental agreement and they dont sign a new lease with me, What can I do? (Aside from waiting 60 days) My goal is to have them out ASAP and cash for keys hasnt worked so far. Has anyone dealt with a similar situation?