How to be an Owner Builder?

[Peyton Millirons]

What exactly is the rule on being an Owner Builder? 

I have heard that you have to wait at least 1 year after construction or remodel to sell/rent the property? 

However, I see house flippers all the time that are obviously not Contractors do all of their own work and then sell the property 6 months later. 

Is it only for the projects that you have to pull permits for? Obviously you can buy and sell as many homes as you like so I guess most of these flippers just never pull a permit during their remodels? 

If an owner builder can do all of this what is the point of even getting a Contractors license?