I'm going to be 26 in May. Dropped out of high school in 11th grade and got a minimum wage job as receptionist/techie in training for barely over minimum wage at a local repair shop. Worked for the owner for roughly two years and went from making $7.75/hr to $22.50/hr while pretty much running the business for him entirely. Fast forward a bit, I met a friend locally that was very do it yourself and liked to refurbish laptops & old gaming consoles. We pinched our pennies, rented a space and went into business for ourselves.
Now my bi-weekly take home is roughly $25-35/hr depending on the time of year(this is our slow time crawling out of the holiday season in tandem with the weather). My suggestion to you is to learn how to fix all manner of things computers/phones/tablets on your own time, if you can do so diligently. Go to school for two years for some applied form of business degree.
My greatest advice is to learn how to make yourself remain billable at all times. Whether you're working part time, minimum wage for someone that owns a repair shop, or you're working out of home trying to kick start this the hard way. If you're sitting back with your feet up, you're wasting time.
But to realistically answer your question, an A+ cert would be the first and in my opinion the only route to go if you truly plan to work for yourself. It's just something nice to hang in the lobby. My partner and I both have ours on display. As long as your clients don't realize they're almost worthless, you're golden lol.