Before continuing, I would definitely check if you'll be accepted for a lease, and ensure you are able to use the car for hire and reward, as some leasing contracts may not allow you to do so. You also need to ensure you have the V5 document, in case it's required when you have the car licensed as a private hire vehicle by your local authority. As for insurance, make sure you get quotes first, and that you'll definitely be covered on a lease car, since you won't be the owner of the car (the finance company is), though you may be the registered keeper.
Another thing about leasing, is that the initial payment may be 3, 6, or 9 times the amount of the monthly cost (i.e. £1350, £2700 or £4050), make sure you can meet this cost in the first month. Being self-employed and new, the first payment is not likely to be 3 months, worth, but 6 or 9 times.