There are many voice teachers out there. Some really know what they're doing and get great results. Others don't. Your voice is a very personal thing. You want to find someone who's going to understand who you are, what you want to sound like and will give you the right set of skills to reach your goals. If you want to sound like a professional, you need professional training. That's why most record labels and management firms routinely send their new talent to well trained voice teachers. (I know, often they send them to me!) As someone who was trained by international stars, had a great career as a performer, been a professor of voice for major universities and teaches working pros in Rock, Pop, R&B, Gospel, Country and all pop styles with great success, allow me to suggest some things for you to consider when you make your choice.
It's not unreasonable to audition several voice teachers. That is, take a lesson or two with each until you find the one that makes the most sense to you. Don't expect to get free first lessons. They are working hard and deserve to get paid. The perspective you gain may be very helpful.
You want to find someone who is not going to ask you to push or strain your voice. The voice makes sound by using the breath. If you try to punch or push your voice, you loose control. It's like playing guitar, you want to be loose and nimble. A lot of singers who push their voices burn out. They actually do physical harm to their instrument. The reality is, you get a full range of control (loud-soft, high-low and the full range of emotions) by relaxing and getting that nimble control. Your job is not to make a loud sound, but rather, a good one.
There are some programs out there where instructors buy a franchise and market the technique of some well known teachers Some of these programs may encourage you to push and build up the muscles. The human voice doesn't work like that. You don't build the muscles of the larynx, you train them to work effortlessly. Again, you want to last. Don't wear your voice out.
I once heard the great Tony Bennett asked to what he attributed his long career. He replied that as a young man, he received training in the Bel Canto vocal technique. He uses the principals handed down for hundreds of years by professional singers and learned how to get the most out of his voice and make it last.
What kind of training did your perspective teacher have? Ask them. There are many pretty good singers who decide to teach. Most just won't have the depth of understanding and the chops a well trained singer will have. On the other hand, I know many well trained singers who are snobs about pop music. They may want to change what you do. You need to find someone who's qualified to give you the tools you need will help you meet your goals.
What does your teacher sound like? If he/she has problems, you don't want to learn them.
Are you singing the music you want to?
Can you feel and hear progress over time? Does it feel like the more you think about it and practice, the easier singing becomes and the better you get? Are you getting good feedback from your audiences and friends? It takes several months to years to fully understand your voice and develop a truly professional technique. If you have a good teacher, you'll see steady progress.
I hope this is helpful. Remember, you deserve to work with the teacher that's right for you. It's your voice and it's your money.