I know I'm very good at taking pics. This is why I have decided to upgrade and pursue a business out of it.
It takes more than believing that you can "take very good pics". You also need to understand the concepts of photography, understand lighting and how it effects your photos, and how the exposure triangle works. I have a strong design background myself, but I haven't started really charging for photography until 3.5yrs into my photographic journey. It's imperative that you understand WHAT lens and settings you use for a certain situation, but you have no grasp on the characteristics of lenses, or how to properly expose shots... yet.
The 'professional' (notice the quotes) photographer you know is using a 7D and an 18-270mm f/3.5-6.3? That's one of the worst lenses to have on the camera, and is nowhere near what a professional should be using. It's a superzoom lens, it has a massively convenient zoom range, but not a master of optical quality in any regard. I would not charge a client for images taken with a lens of that caliber, as it would be a disservice to them, and other photographers. I'd use it for a leisure lens, when you don't want to swap between primes. To couple a 7D with that lens is borderline blasphemous, as it's capable of so much more if it had good quality glass in front of it.
Imagine buying yourself a fast, agile, and sexy Porsche 911. Then taking the Porsche to an automotive shop to put a Geo Metro 3cyl 1.6L engine in it, AND THEN beating the body of the Porsche with a baseball bat. That's the real world equivalent to what's happening on the "professional's photographer's" camera.
To be completely honest with you, you're way in over your head. You need to step back, and think about this.
You say you have a degree in design, so let me use this as an example... What would you think of someone who has had no design training or coaching that goes out to purchase the Adobe Design Suite (PS, InDesign, Illustrator, etc.), and decides they want to be a graphic designer? They will start promoting themselves as a designer, and charging for designs. They won't know how to effectively use any of the immensely powerful programs at their disposal, but they'll wade through tutorials on youtube and scare something up for the client. It won't be good. As a matter of fact, it will probably be downright terrible. They won't know how to charge their clients for the amount of work that they're doing, because they've had no business experience.
My suggestion to you, would be to start out with a 60D with a kit lens and an 50mm f/1.4. If you are really serious about photography, that will give you a great start.