I'm only making assumptions so I apologise in advance. 15 regular clients and new to this ?. I'd reckon on you needing a 60 ft pole that you probably haven't got ( to be fair most of us don't ). They're not cheap. Doubtful you'd have many other jobs you'd need it for. Even at the prices experienced willy wavers are quoting for this, you'd have to clean it several times to even break even and pay for the pole. In the current economic climate and pandemic , I'd only consider it if I already had the kit to reach it. Sorry, but I think it's a non starter. So many easier residential jobs out there to clean without having to invest in a pole for such a height.