I did all sorts before I started window cleaning in 1991.
Builders' labourer, bakery hand, kitchen porter, printer's assistant, multi-drop driver, nursing assistant, advertising merchandiser. Quite a variety there - though the print work lasted the longest (13 years). I liked the advertising job too bombing around the southeast in someone else's van and only seeing a boss about two or three times in a year. That was what gave me the first clue that perhaps self-employment was for me. Nevertheless, when that job folded, I went on the dole while looking for work (the job market was very difficult then too). I started window cleaning out of desperation really. I had a Datsun Cherry hatchback that was on its last wheels so, with the last of my money, I bought a few tools. Even the ladder was borrowed. I knocked doors from zero turnover. I only intended to do it until I got a "proper" job. 20 years later, I'm still at it. It was getting very stale though but 6 years ago, WFP gave me a new lease of life. Happy to do this until I retire.
The beauty of window cleaning, especially if you use WFP, is that you can earn something reasonably decent even if you do it part-time and study on your time off.