Hi I have not long started working from home/ mobile and am in the process of building up my client base. One of the first things you must do tho is get in touch with your local council to make sure that there are no restrictions to you working from home. I had no problem at all, but all councils are different some actually charge a fee for planning permmision, and they look at parking issues etc, also if you own your own home your mortgage company and insurance may need to be informed...You have a three month leeway to inform the taxman that your working self employed.
Asfar as advertising, anywhere you can really friends and family are a great start, and word of mouth is the biggest client grabber. always make sure your own nails look good your your own best advert...and leave your buisiness cards everywhere you can.
HTH Suze