Contracts are generally available on 24 - 60-month agreements, usually the longer the agreement, the lower the rental but on occasions shorter agreements see lower rentals.
It is important you are comfortable with the contract length, to exit the agreement early will incur a cost (usually 50% of the remaining rentals). If you take on a shorter contract you can then extend it for an additional period.
You will take a contract based on a set annual mileage, the more miles you do, the higher the rental, you do not need to worry if you do more mile in any given year as long as the total mileage in correct. For example, if you take a 3-year contract based on 10K Per Annum as long as the vehicle is retuned on no more than 30k total mileage it is fine.
Most funders will though give you the option to change your mileage in the event your circumstance change.
If you return the vehicle over the agreed mileage, you will be charged what is called an “excess mileage charge” this charge is not to penalise you but to offset the detrimental affect it will have on the resale value.
If your excess mileage charge was 10 Pence per Mile and you returned the car 1,500 miles over the agreed mileage the excess mileage charge would be £150.00 +VAT.
In summary the contract length and annual mileage impact the rental it is important you choose them accurately, remember though you do have the option to amend should you need.