Finding an authentic ikebana teacher can be difficult. Over the years, I've talked to people who state that they are ikebana enthusiasts and are happy to teach others, but their ikebana is a self-styled ikebana and not one that is a continuation of a teaching and practice tradition of many, many years. They basically do what they want and there is no critique of their work. This is unfortunate because a self-styled ikebana practice has a tendency to be stagnant and can lack depth and creativity. Also, people looking to learn the art of ikebana would not know what to look for in finding an authentic teacher who has a depth in their practice of ikebana that truly expresses the essence of this art form.
When I come across someone who states that they do ikebana, the first thing I ask is with what school of ikebana are they taking lessons? Ikebana is a lifelong practice. One is always growing in this art form. And a teacher of depth is also continuing to learn. The next thing I'll ask is how many years have they been taking lessons. Knowing who their teacher is and being able to see their arrangements is also important. They may be an accomplished teacher, but that does not mean that one will like their style of ikebana. Another question is are they attending any ikebana groups and doing demonstrations or how many they are teaching or how long they have been teaching. It is important to keep one's skills up and only doing ikebana once or twice a year, and not participating in exhibitions can result in a stale practice of this art.
Most importantly, the one thing to ask, if one is serious in taking lessons from this person, is to see their school's certificate to see if they have been authorized to teach. If they don't have such a certificate, I would look for someone who does.
Before one takes up the art of ikebana, it would also be wise to get a realistic sense of how much time one can spend on it. A life full of many other activities which may interfere with a regular practice of this art, may make it difficult to progress.