Hello, I have been living full time as a yoga teacher for the past 5 and half years. I've been practicing for 12, and teaching for 7. I lead TTCs, and have previously owned my own studio. Here are some observations from my experience and witnessing other teachers make a living as yoga teachers.
1 - Most teachers struggle financially for the first couple of years. No college student typically lands their dream job right out of school, and the same applies to yoga teachers. For these first couple of years, you'll develop your skill and your voice. Look at all the unnecessary expenses in your life, and downsize. It is not a reasonable expectation to maintain a lifestyle that might have developed prior to teaching yoga. This can be a humbling experience, and an opportunity for growth.
2 - Take every opportunity to continue learning through every avenue available to you: Additional TTC, workshops, retreats with good teachers, a mentorship with a senior teacher. Your 200 Hour TTC establishes you with the minimum qualifications to teach yoga. You'll need to learn a lot more before you can offer more than drop in classes at a studio. When you develop the knowledge and confidence to teach workshops, host retreats, and offer specialized courses, then your financial successes in this profession will improve.
3 - You must be an entrepreneur and consider this a business if you want to teach yoga and be financially stable. That means you must learn to market yourself, take calculated risks, and sell your services for what they're actually worth. Too many teachers are afraid of money, and offer their expertise far below value and even for free.
3.5 - As an addendum to being an entrepreneur, the more unique your offering, then the easier time you'll have marketing it. It's easier to market to a select smaller niche than it is to market to everyone. For example, I notice that the original poster of this thread is of an older demographic. Having a program aligned towards older populations, new to yoga, and with physical limitations separates you immediately from the pack of general jack-of-all-trades teachers. You'll stand out from them.
4 - Maintain your practice, and allow the lessons from that practice to permeate all aspects of your life. I used to think that I would never obtain the splits pose, hanumanasana. I said "I have guy hips", it will never happen. However, this did not deter me from practicing the pose. I practiced it anyway. The end result was not my goal, but rather the work of the pose itself was for its own sake. Low and behold, a few years ago I found that I could get pelvic floor all the way down now in this pose. What I learned along the way was not the splits, but the cultivation of persistence, dedication, and devotion.
Now, take this same perspective and scale it up. Don't set out to teach yoga simply for the money. Teach because you have a calling to, and you love it. Don't allow your lack of success to deter you from your effort. Keep awareness of where you want to be, and continually move in that direction day after day, week after week, month after month, and even year after year. One day you'll look around and be amazed at where you wind up.
None of the successful teachers you know got to be where they are without years of effort, trial and error, and ups and downs.
It is still better to do what you love every day and just get by, than to be amazingly successful yet hate your life.
5 - Read, or re-read the Bhagavad-Gita. Everything I mentioned in point #4 is basically a summary of the lessons contained in that book.