if your pretty fit and like working outside(ive worked outside since i was 13 on farms,nurseries,landscaping.)and have self motivation then it could work.
the reality is that many dont last as its hard manual work and can get tough at times during the winter months due to bad weather,then theres no holiday pay,sick pay etc,etc.self assessment and tax,insurances to sort out.
theres more to window cleaning than actually cleaning the glass thats for sure!
i love it most of the time but its took years to build a half decent round with loyal good paying customers.it is a simple business to run compared with a lot of others though.
best wishes and good luck!hope you like canvassing!!

dazmond