It seems to me that in my city there are really not enough yoga teachers. I've been practicing yoga for several years, and I'm sure that I could become a good teacher to help people come to a balance.

This is a big problem because this is the logic that guides most yoga teachers. I believe it's important to be a certified yoga professional who knows all the ins and outs of yoga teaching. I found 2 cheap online yoga teacher training certifications here. You can compare options to choose the best and get trained, but in any case, each of them is accredited by the Yoga Alliance.