If you were selling a business, say something like a retail outlet of some kind, the average price to purchase now is 2.5 times the annual turnover. But it always comes down to what someone is prepared to pay for it. If you have van's, work, staff and accounts ect are all up to date, might be worth to get a couple of valuation companies in to give you a price. The best thing is with window cleaning, you can effectifly just go out and be earning from day one, but with a shop you are going to have to keep advertising your goods, and the people that do walk through the door there is no guarantee they are going to buy your goods! IMO, a lot of window cleaning rounds are under valued.