One of the documents you will need, when applying for a long-term residence permit, is a letter showing that you have not received government social assistance (welfare) in the last three years of your residence in Turkey. Here's how to get that letter.
Go to the Sosyal Yardımı Ofisi (social assistance) office. This is usually located in the Nüfus (population directorate), or the Kaymakamlik (district governorship) building in or near the city or town center.
Large cities with multiple districts may have one of these offices for each district, so you will need to find the one responsible for the area where you live.
Give them your residence permit, which has your kimlik numarası (identity number) on it. They will use this number to look up your record.
Ask for a letter, on official letterhead, stating that you have not received social assistance for the last three years. This must be on official letterhead, and not on a regular piece of paper.
Long-term Residence Permits Forum: Have questions or want to make a comment? You can do so here.
Turkey Residence Permit Law (PDF): The Law on Foreigners and International Protection, Dated April, 2014. In English, this is the Turkish law which governs residence permits.