It’s a very competitive market, you’re right.
Several years ago, I self taught myself social media marketing (Facebook/IG), web design (WordPress), and graphic design (Adobe/Canva). I’ve had my own “marketing business” in the past, but saw little success with multiple, albeit short lived attempts. The biggest hurdle I’ve encountered is people being unwilling to work with you because you’re a new company. It takes time to build a name for yourself.
For things like SMM (compared to web or graphic design) it’s harder to “show” your work. When you’re new to the field and have no portfolio, you can just create dummy websites and mockup designs to show your skills. With social media it’s a lot harder because it’s more so based on results (engagement) than looks alone. Customers need to be able to visit your previous client’s Instagram account and see healthy activity.
I’m not sure what kind of area you live in, but I highly recommend you offer your services at a heavily discounted rate, perhaps even free before you start thinking pricing. This way, you’ll have something to show other customers down the road. You can always start charging more as you learn more and produce better results. People may still be apprehensive towards hiring you depending on where you are and what the competition is like. It’s important to understand that you have to be persistent. Hearing NO from potential clients is very common in the early days of service based businesses.
As for me, currently I am pursuing a degree in communications and working a somewhat related job that has taught me a lot and will look good on my resume. Before you jump head first into this venture, I encourage you to work an industry related job or get an education. Both of these will play heavily in your favor when you do start a marketing business. Best of luck!