Definitely agree with most people you can definitely utilize your skill as a designer and provide your services. That will be a good business for you to start with because you are already experience in the field. Also is something you most likely have a passion for as well.
Stick to what you are good at! If you are a designer and you are really good at it, start your designer business. Don't worry about people charging lower fees, it is the same with every niche, as long as you provide a really good service you'll always find people that will rather pay a bit more for complete satisfaction and a professional service. The most important thing is to stick to what you are really good at doing and what you enjoy! It might take some time but once you get your brand noticed prices won't be an issue.
You mean Interior designer? You can try online business such as blogging or create a website that share about knowledge especially about designer and you can put PPC like adsense or other
Take part in design contests as well as do design work for other people. All the while build a site around designing. Maybe write new tutorials in photoshop or blog about a new tutorial you have found. like 10 best photo editing tutorials everyone should know. Slowly build traffic. If you have traffic you can monetize it later in various ways. You can also sell your photos or designs through istockphoto.com or similar sites. Options are endless you just have to act and stick to it.