First off, I’m super excited for you. I wish you all the blessings on your journey of faith. It’s just as much a blessing for me to see young people inspired by the promise of our Lord and Savior Jesus Christ.
I have to commend you as well for asking such a thoughtful question. This is a big deal, a big decision, and to ask this question shows a lot of humility and maturity on your part.
I think age is relative to the point of his maturity in our faith…I would say.
Our Catholic Faith is a big world. Just learning who is God, Jesus, and the Holy Spirit is a lifelong task in and of itself but learning what our Catholic Faith teaches us with regards to interpretations of scripture, our catechism, our traditions, etc adds a ton, but is very important in discovering Truth!
Don’t let that scare you. I am the RCIA coordinator for my parish and I have a lifelong amount of learning and discerning ahead of me too. Growing in faith is a process.
Furthermore, RCIA is a very important step in this journey but you can’t learn everything about our faith in that period. The RCIA process itself is not meant to have a set time table…So don’t feel rushed or pressured to get Baptized and or confirmed by next Easter. =)
If this young man, your friend, whom you are considering as your sponsor is practicing our faith in alignment with our beliefs as Catholics, I would personally be okay with that.
Is he part of the RCIA team for your parish? Not knowing who he is myself, I might suggest you do as @otjm suggested and ask your RCIA team about him.
It’s one thing to have trust and a comfort level with your friend but another thing to make sure you are getting authentic Catholic teaching. To put it plain and simple. How do you know what he is sharing with you is right? I’m making assumptions but its the question I think you are ultimately concerned with.
If he is discerning the priesthood, then perhaps he has also spoken with the priest at your parish. I would ask that priest too.
Age is relative. We have younger people who sponsor older people all the time and vice versa. As the RCIA coordinator, I would try to discover a few things about this individual before I make an assessment. If he is as you describe him, I wouldn’t see a problem.
Hopefully, that was helpful be it long-winded.
Peace & Blessings