Car rentals do have certain restrictions that apply, and it is always important to know the contracts and to know what you are and are not allowed to do before signing the agreement. While individual contracts may vary, and it is always important to read each individual contract you agree to, there are some basic common limitations with all car rental companies, and some others that are common enough to be worth asking about.
A common restriction actually involves age. Most car rental companies will not rent a vehicle to someone who is under 25 years old. There are a few who will rent to individuals who are between the ages of 21-24, but be prepared for an additional daily fee and possibly a longer list of restrictions than before. One restriction, at least from United States rental companies, is that taking the car to Mexico is never allowed. In addition, the far majority of rental agreements clearly state that the car should not go on any roads that are unpaved, whether gravel, dirt, or otherwise.
Generally, the car you rent needs to be returned to the location where you originally picked it up. There are some exceptions, though these matters should be...