Between 18-30, depending on your & her maturity.
Qualify a potential wife first by intelligence & make certain she is family-oriented.
Have all your children before 35, for richer or poorer.
When the children come, embrace them and live for them & your wife.
Put no temptation before your eyes once married. Don't screw it up, ever.
By the time the children are grown, you are still young enough to enjoy life.
If you can do this, you have lived in paradise on earth.