You can start up trad from around £200.
As said, unless it is in your contract that you may have to work weekends, your time is your own, and this would be a good time to set aside for cleaning the houses you pick up. It is also a time when many people are off work as well so you are more likely to be seen and asked to do theirs.
Do you have time available during the week, ie evenings, for canvassing? Also, have you done window cleaning before? I'm not trying to be patronising, it's just that it would be good to practise on your own and family's windows to build your confidence.
Best wishes,
John