As usual with car hire, to minimise risk to your blood pressure, it is a good idea to ask in advance what extra "local charges" will apply - such as "winterisation".
You may find that the advent of winter may not have been anticipated when you made the booking.
Pirin Owners have successfully used the following firms from Sophia Airport.
Tyre damage is often excluded from your insurance, so be extra careful about hitting pot-holes, and if hiring from one of the "smaller" agencies, give the tyres a look over when you pick up the car.
On one occasion we were supplied a car with a slow puncture. We drove to nearby hotel and stopped for the night. In the morning we couldn't put our finger on why this heavily laden car was so sloppy to drive, until we found that the tyre had only about 0.5 bar in it!
Other owners have had cars with poor wipers and low washer water.