Yip, sure, and what practical way or method do us Joe Bloggs have of measuring our own personal "natural limit"? Ive seen various calculators online (Casey Butt has arguably the best) but at the end of the day these methods are crude and non-specific to you (and me).
Common sense would suggest that you train for some time, experiment with different programs, trial diet manipulation, and in doing so find out if this discipline is something you enjoy and see yourself sticking with going forward...then consider PEDs.
We can argue 2 years, 3 years, 5 years training and trialling as a natty, but theres no black and white line that you suddenly cross and become "ready". Its ultimately a personal choice. The guy who trains 10yrs natty before touching gear is not "better" or more ready than someone who jumps on after 3, theres a million different reasons why they did things the way they did. A universal standard is arbitrary bollox.