Cas,
good luck mate and if that was anywhere near me mate i would be seriously interested.
some people are cut out to be window cleaners, some people have a good business head, but combine the 2 and it could be serious money, if i was you i would:
I know what you mean when you have had enough and want to concentrate on your new interest, but seriously why dont you sell one van and the bulk of the work,
and keep the smaller van with enough work to keep someone going for 2-3 days per week, pay them well so they look after the work, or even rent them the van and work, take a percentage and tell them whatever extra work they pick up they can keep so long as you always get your agreed percentage = that way they have major incentive and also will look after the work as if its there own.
That way you will always have some money coming in, and if things ever went not as you have planned, you could always fall back on the window cleaning = that way both your gym and the window cleaning would grow together.
Just think you could even have noticeboard in your gym offering members reduced window cleaning, gutter cleaning, jet washing etc
and also offer your window cleaning customers cheaper gym membership, and i reckon you would be on to a serious winner straight away.
Thats DEFINATLY what i would do if i was you !