If you wear work clothes they are a work wear,, they are a fixed cost, if you run a vehicle for work that is a fixed cost, boots gloves, jackets, hats, socks, gimp masks, tea coffee sugar sweetener, these are all fixed costs.
If you buy a car for 5k without any prep and sell it for 7k you don’t make 2k minus VAT & tax, you have to know your actual running average fixed costs.
You don’t have public liability? You don’t have an office at home, you don’t travel to auction you don’t have a computer, you don’t have a printer, you don’t have ink, you don’t have pens, you don’t service your allocated car, you don’t have break down cover.....