Angel, one can use a shovel to cut a nice edge between the lawn and a flower bed. Dig out a scoop 3 or 4 inches deep all along the edge and mound that dirt in the flower bed. No need for edging at all. If the edge starts to look ragged you can repeat the procedure.
Abraham, I wonder whether you are allowed to do freelance work in addition to a job. The idea being your job pays the employment tax while you are building your business. When you have enough clientele leave the job. There is definitely a market for skilled gardeners but having support as you develop your skills and find your niche would be nice. I would and do avoid all of the chemicals. Where I live I need to be licensed to use these on a client's property and then use them according to the label. This means no vinegar for weed control. It works out, most of my competitors use the cides. I market my squeemishness with chemicals as an organic approach. I do aquire significant quantities of weeds which need disposal. You will want to have a place to compost. Or maybe rabbits. If you get certification from an educational institution it will help you approach clients who can afford more exciting projects but there is no substitute for hands on experience. Get started, you will learn as you grow.
I started in business mowing lawns. The shrubs and flower beds weren't my responsibility. I developed a niche for my mowing business by learning to take on these extras, many of my competitors don't. I learned quite a bit from aging homeowners who have hired me. I now have clients who I design, install and maintain flower beds for, as well as the mowing. I have never had a client asking me to grow veggies. I think it might be possible to find clients who will pay me to grow organic produce in their own yard rather than paying at the market. I'm sharpening my skills with veggies as I figure it out.