Yes definatly need one.
The majority of people these days are on-line and do shopping ect on-line.
When it comes to commercial work when the Boss of a company tells his secretary or who ever to find a window cleaner, the first place she's going to go is her computer!
You have to move with the times.
A website is a lot of hard work and loads of hours on a PC to create, optimise and maintain but I for one feel its worth it.
Mine brings in around 2-5 jobs a week, usually spread out but always takes me to area's that I hadn't canvassed so double wammy and its only been up and running for the last couple of months or so...
http://www.cthruwindows.co.uk