hi there i have a website i wouldn't say it generates a lot of work but it does give potential customers somewhere to go to find out a little more about you and your company.
If someone is looking on yell.com for a local window cleaner you can get a free listing with yell.com and from there a link to your website.
also Google if someone local to you searches window cleaner you can get a free listing on Google maps with a link to your website.
you can track this in Google analytic's to see the performance of the site.
this month 1 of my websites has had 117 visitors and another one 48 visitors i can tell that where them visitors came from so out of the 117 33 where from Google searches 22 where direct 21 from Facebook 6 from yell.com and the rest from other free directory's
its well worth having a website for what it costs. you can easily build a website yourself i had my brother in law build mine and it was taking so long to get changes done that i got fed up waiting and looked into how to build one myself now i have built 4 and forever changing them they started out a bit s**t but now i think they are ok. although i don't think i will ever be happy with it lol