I will take students as young as 5 years old on piano, as long as they know their letters A-G and numbers 1-5. It is also very important that they know their right hand from their left. For all other instruments I prefer to wait until age 7, except in special cases. It is never too late to begin lessons, when you retire is a great time to start because then you probably have more time to practice.
I believe in tailoring the lessons to the student's wants and abilities, not everyone is taking music for the same reasons. Music lessons should be fun and interesting as well as educational.
In addition to my private lessons, I also teach music classes at the Bastrop Christian Homeschool Coop for the past 5 years, and have taught private lessons at various Christian schools in Bastrop in the past. I taught lessons at Owens Music in Bastrop from 1994 until the store closed in 2010.