The most important thing that the contract should specify is the rent, and, equally importantly, the currency in which you will pay the rent. For many years, landlords preferred rent in foreign currency (it was more stable than the Turkish lira). Now they are more willing to accept lira from foreign tenants. If you do pay your rent in foreign currency, be aware that your landlord may try to raise the rent on you if the lira´s value drops sharply. Having an exact amount specified in the rental contract gives you negotiating leverage.
You should try and have the length of your lease included in the contract, though some landlords may not see this as necessary. If your landlord does not specify a particular lease length, assume that you will have to renew after a year.
Landlords do pay all taxes on rentals except for environmental tax (çevre temizlik vergisi), which tenants pay with their water bills.
Landlords have some exceptional rights in Turkey: if a landlord or his family want to move into his property, for example, he is allowed to evict his tenants without notice. Landlords are also allowed to evict tenants if they miss two months´ rent. If the landlord sells the rental property while you are living there, the new owner is also entitled to evict you (though he must give notice first).
Disputes with your landlord
While Turkish law does, in theory, allow you to take your landlord to court over disputes, don´t even consider it unless you feel that you have been grievously, obscenely, gratuitously wronged. These lawsuits proceed at a glacial pace. The law also claims that landlords are responsible for keeping rental properties in safe condition, while tenants are obligated not to cause damage. There are few practical resources available to enforce this provision, however.
All this means that you should take special care when renting. If your landlord seems strange or strikes you as unpleasant, look for another property rather than take a risk. You might miss out on what looks like a dream apartment, but in doing so you could very well steer clear of a rental nightmare.
A note on contracts in rural areas
Contracts in rural areas are often much less formal. Many landlords consider an oral agreement just as valid as a written contract. Try your best to get them to agree to a written contract.
If this is impossible, make sure that you discuss the rental arrangements in detail, discussing everything you would find in a written contract: rent payments, rent currency, lease length and any special stipulations. Have a Turkish friend translate for you if your Turkish is weak. Country rentals often require a deposit of as much as seven months´ worth of rent, but since the monthly rent is so cheap the deposit will usually still be less than a security deposit on a flat in the city.
In rural areas you will probably find even fewer legal resources than even the limited number available in the cities, so it is important to be clear on all elements of your rental agreement.