Traders are really struggling to source good stock at the moment so this isn't surprising. There's nothing to be wary of, really – just treat it like you would any sale. Don't release the car until the funds are in your account and print off a receipt for both of you to sign (this one from the AA covers everything: www.theaa.com/car-buying/buyers-sellers-contracts). Use the DVLA's online service (between the hours of 7am and 7pm) to inform them you've sold the car into the motor trade: www.gov.uk/sold-bought-vehicle