Before you start any potential purchase, you need to be certain that the equipment you have selected is what you do really want. With leases, you will have a minimum term for keeping all equipment and if you change your mind a couple of months down the line, it will be too late.
With most contracts, you will have perhaps a seven day cool off period but after this, it is classed as ample time to change your mind and contact the company in question. Always be certain before finalising your choices, once you have there is no going back.