I rented a car from Fox via telephone from NYC before I got to Budapest. The day of the pick up they came with a contract that charged me a hidden fee (not disclosed on their web site or over the phone) of 500 US dollars. This was supposdley a "Rental Fee". Then they continued to tell me that the contract will allow them to charge my credit card 2 months after I had returned the card. I dont know why.
I had a good Hungarian friend who called them to inquire about this outrageous FEE. After the call, they did not charge my card the hidden fee.
If you decide to rent with Fox asked them to send you a copy of the reservation and the contract prior to getting to Budapest so you know exactly how much you will pay at the end of of your usage time.
I will suggest to come up with the extra money and rent from an international company and avoid the surprises, hidden fees and tricks that could ruin your vacation. It certainly upset me for the first week, until my friend made that phone call.