Its not the cleaning that takes the time. You can make very good money cleaning.
It's waiting in the bloody shop to get paid!
I do 23 shops each week mainly on a Friday. Some are just straight forwards - do the outside windows and that's it. Others want the shop signs done weekly, or monthly, some have upstairs windows and some have the insides done weekly, fortnightly, etc.
Sometimes I get asked for odd other jobs to be done like mirrors in a hairdressers, or all the counter glass both sides in other shops and so on.
One cafe/restaurant wants the whole works done weekly, insides, outsides and entire frontage.
Sometimes it's easier and quicker to do some shop outsides wfp in the evening when there's less people about.
I invoice most shops every 4 weeks rather than weekly. A few I invoice every 3 months. Sod going in weekly for the cash.
Not only is it highly profitable, I enjoy the change from houses every Friday. You get to know all the staff, get to know their world, have a bit of a laugh and I get free food or discounted stuff in most of them.
Over time, do a good job for one shop and you'll pick up work by just doing that and being there each week. Owners/staff in shops know all the other owners/staff in other shops near by. If you're cheerfull and do a good job, you'll get more work but it takes time.