When to start investing with Primary Residence equity?

[Joey Signa]

Hey everyone, this is my first post after consuming as much about REI as i can take. I am a licensed Realtor and have just started my career in Charlotte, NC but want to start REI as a retirement plan.

My question is how much equity should I have in my home/do i need to start investing with it? When is it start or dumb to pull it out? 

Is there a common percentage that is used to know when to start leveraging with it? For example, should you always leave 20% equity in and pull out whatever is over and above? 

Thanks so much!