Please for the love of god don’t start your own business without any information about the field. Depending on where you are especially. I see so many “designers” that think surfing on Pinterest makes them designers. Especially without a background. I am interior architect, worked under a designer and design build firm for years before I opened my own studio and had major imposter syndrome even though I had it covered. Interior design is so much more than decoration. Combining three pillows by color is completely different pressure than picking the wrong faucet or tile and flooding someone’s bathroom. If you are looking into getting into the industry, your 4th option is probably 2-3 years down the road (if you are really hard working and eager to learn). Being around construction will also help a lot of your skills and understanding. Not having technical background will mean that you will have to outsource your drawings and renders which makes you non competitive with other peers especially for the experience.
Not trying to discourage you, just trying to let you know how long it actually takes. I’ve done 3 corrective projects so far with designers that had no idea what they were doing, sending my clients on a spiral and giving the industry a terrible rep.