The type of vehicle that you purchase should comfortably fit to be used as a cab. Being a business entity, you will be concerned about maximizing your profits and thus you need to purchase fuel efficient cars. The rear seat should definitely be comfortable and it should have enough cargo space to carry the luggage of a passenger.
While starting a cab company, you should always have your profits at the forefront. You can decide to purchase new or used cars for the business, but used cars might be cheap but will only be effective in the short run. Used vehicles also cost a lot more on the maintenance bit and it is important to always check the mileage and general condition of the vehicle before purchasing it.