I have a customer at the moment who lives in a large house in the sticks. She spends much of her time abroad. When I clean, I email her the bill and she sorts it out by BACS. I've always been paid within 48 hours.
Technology makes it so much easer to run a window cleaning business these days. When I started (1991), I used to get cards and bills printed by a machine at the stationery shop for extortionate rates, any pre-arranging had to be done by voice over a landline and was very hit and miss about whether they were in or had an answering machine (one of the reasons I still have few pre-arranged jobs - it just became a habit) and written communication was by post. The (very few) BACS payments had to be set up by telephone banking because internet banking just wasn't around. Record keeping was hand-written and even when I first did it by computer, I needed an ancient Amstrad PCW spreadsheet called "Rocket" (ha ha). Only 6 months income could fit on a floppy disc (it had no hard drive) so that was six discs for each year - two for income details and one for expenditure (x2 for back-ups) and it took an eternity to load.
Additionally, I used to have a metal thing which consisted of two long lengths of metal joined by many shorter lengths and had to climb up it.
And you try telling the young people of today that and they won't believe ya.