It’s actually quite difficult to start this kind of business from scratch. The most successful designers I know started off with a franchise (Interiors by Decorating Den, for example) which is a large initial investment, but has many perks. They set you up with an established list of vendors which is really beneficial since you will have to work very hard to establish a relationship with a vendor on your own. You get all kinds of collateral and advertising assistance, a zip code or two in your area to market to using premade flyers, postcards, etc, a website to personalize, a national support network of other designers and professionals, training seminars, events, access to design marts, and on and on. It’s a great way to get started but like I said, a large initial investment.

Sometimes you can buy out an existing franchisee/designer who is retiring and get all her customers! That’s a huge help to a newbie who doesn’t have large client base.

Other than that, you would just have to pound the pavement, find ways to market yourself and start making alliances with vendors so you can get goods at reasonable prices. With an established franchise, the vendors will give you the lowest prices because the franchise as a whole is “buying in bulk” even though you yourself are not, see? So, it’s very beneficial in that way. I would suggest that your mother get some formal training, make a portfolio of her work and start talking to practicing designers to get some advice. She may be able to work as an assistant for a while to gain some skills and confidence and then transition into her own business. Or she could try to land a job at an interior design firm but that could be difficult given the amount of highly trained competition out there.