If staying with a relative or friend who lives in Turkey a notarized Invitation Letter from the host with their contact information, purpose and duration of your visit, conformation of where you will be staying icluding the full address, signature and date. You must provide proof of hosts status in Turkey, i.e copy of passport, residence permit and national passport details page if they are not a Turkish citizen.
You will be required to upload a copy of your Invitation Letter when completing the visa application.
You must also send a hard copy to Traveldocs.