Easiest way is to work out roughly how long it takes you to turn your stock. So lets say you price your cars keenly and on average it takes you 4 weeks to shift a car. You will be selling on average 7 cars a month. Lets say a hopeful average £500 profit per car so £3500 per month gross. Minus expenses and Vat and tax you would probably be netting no more than £1500 per month so around £18000 a year. Realistically it could be more like half this amount so not much more than minimum wage !