When I sold up and moved to Ireland 3 years ago, some well meaning friends here who are also window cleaners (albeit mainly commercial) felt really sorry for me, telling me that if my target market was residential, I wouldn't stand a chance. The country was in a real pickle economically, and people were losing their jobs in droves. I was nearly 50 years of age then as well, and knew I had no other viable options but to get out there and make it work.
I methodically planned out when and where I would canvass, and armed with a steely determination to succeed, coupled with the 14+ years experience in the game in the UK, I went out knocking doors within a week of arriving.
Three years on, I consider myself to be established. I am picking up new work every week, some of which I have no idea where it has come from!
To the OP, it is possible to build a window cleaning business, but it takes a lot of determination and hard graft, and there will be setbacks along the way. There is a lot of competition out there, and some customers will mess you about for fun, so it will take a few years to build a decent run.
The advantages are that you can decide when and how you work, but this has to be weighed against the disadvantages of no holiday/sick pay and dealing with bad weather and equipment failure/maintenance and other factors which bring about downtime. But if you are determined enough and self motivated, you can succeed.
Best wishes,
John