As someone new to the server it has been a big help to have a rental but have quickly in 15 hours of game time managed to get my own car and roleplay into a business. I agree with the comments, they should be for brand new players to get them around in their first steps. My idea would be:
-Remove them as an option after 40 hours of gameplay, or increase their rental price to be more in line with the economy.
I have done a few hours of taxi work now and while sitting at the airport it's almost impossible to get fairs as rentals are so much cheaper and affordable, a starter vehicle is a nice boost to the player and gives them more freedom and access but I think it should be limited to starting your journey.