Get married before you become a full time marriage counselor.
You really don’t need to be married before you teach and counsel on premarital relationships. There are a lot of things that can be taught ranging from understanding your purpose, chastity, character, compatibility, values, courtship, discipline, focus, resourcefulness, and a plethora of others.
Leave the weighty matters of husband and wife relations to those who have the wisdom of God tested and proven by some measure of experience and time in the arena of application.
In time when you get married, you will see things clearly, and some perspectives you held as a single person are very likely to shift; even your approach to issues will definitely be different.
In summary, as a single person teaching relationships, know your limits and stay on your lane.