You do not need residency to buy or sell a vehicle. Last year the Notary Offices changed their software without realising that there was no space to put a foreigners ID such as passport number or tax number. As a result they just told people to get residency as they could not be bothered to go through the long winded process to get around this. Notary No 2 knows the problem and how to get around this so go to them. This information was given by Koray Atak of Atak Services in Fethiye, he is generally correct in all things legal and if you have a problem then contact him, or his wife Gunes (pronounced Gunesh)who will guide you through the system.
We insured our car last October, no residency no problem. We have just returned from Bulgaria, driving there and back, got the insurance Green Card from our insurer no residency no problem. You do need residency for travel insurance (holiday type) and medical insurance with some companies.
Once again-you do not need residency to buy or sell motor vehicles!