Not sure how effective Facebook Ads are for lead generation, as my experience is purely based on search generated leads from Google Ads, but I would argue leads from Google are higher quality, because they are actively searching for the service, rather than stumbling upon an ad as on Facebook.
I'm happy to run a test campaign for a window cleaner, who would be interested generating extra leads, and I won't charge anything for doing this, as long as you are willing to cover the ad cost.
And we won't go for any crazy amounts, like £1000/week, which sounds a bit unrealistic to me for window cleaning, unless you are advertising nationwide in the UK.
Stephan