There are several companies in the market. Some have a large fleet while others operate with just three or four cars. Try getting the latest model as the older the model, the more mileage it would have done. Usually, the rate for a sedan is around 1800 per month but this can vary from company to company and from brand or size of the car. Most rent-a-car company will ask for a credit card without which they will not allot you a vehicle. I suggest you be patient for a few months and put up around QR 25000. You may then be able to get hold of a second-hand car in good condition within that amount.