If you are an EU citizen living in Turkey, you are perfectly entitled to start your own business.
You must apply for a certificate issued by the Central Commercial Registry at Antalya Ticaret Odasi confirming that the business name you intend to use is not already registered with them.
You will also require a tax number 'Vergi numara' which is a number given out by the tax office to enable your business to pay the necessary taxes.
In the UK businesses are registered as being a Limited Company, Public Limited Company etc and there is a similar system in Turkey. You should seek expert advice from a Solicitor or Accountant as to which of the Turkish systems would suit you best.
You must register your business with your local municipality and obtain a' Isyeri Acma Ruhsati' which is your license to trade.
Foreigner owned business, must also register to the Turkish Revenue Administration which is known as the GIB Office. If you are not completely fluent in Turkish and confident with filling in all of the complicated legal forms, you should seek professional help with this process from a Solicitor or Accountant.
If you receive any form of income from Turkey, even if you are not a business owner or living in Turkey permanently, you may be liable to pay some tax. You should seek advice about this to avoid any fines or problems in the future.
As already mentioned, if you buy a second hand car with debts attached to it, make sure the seller zeros the debts so you don't end up paying them. The same applies to buying an already established business. You must seek legal advice to have all necessary checks carried out on a business before buying it.
Effective Feb 2012 the new Social Security Law for foreigners, all business must make social security payments and these funds contribute towards local services such as health care facilities. If you contribute for 15 years or more to pay social security monthly installments, as a foreigner you qualify for a pension in Turkey when you retire !