There is very, very little doping in domestic cycling. The furthest it typically goes is Phentermine or other weight loss drugs. A rider making $10-50k/year can't afford to dope.

How to become pro? Win a lot of races, upgrade to cat 1. Get on a good amateur team that can do bigger races like Fitchburg, Nature Valley, Air Force Classic, etc. Do extremely well -- like best amateur rider (non-pro license), etc. Make a lot of friends who are pros. Junior and U23 nationals are a big plus.

Then, look to sign to a smaller pro team. Do really well and you'll eventually get noticed by bigger teams. Even many of the top domestic riders never get the chance to go pro in Europe, and rarely do they get to the top in Europe. Eg, Ivan Dominguez was arguable the best domestic pro sprinter in 2007 and 2008. He went to a ProTour team this year and made it 6 months before they mutually ended their contracts. He couldn't perform. Although good at sprinting after a 90min crit, he couldn't do 90-110+ races -- especially day-after-day.

The other option is to dominate a few European races. That's a quick way to be signed. Then again, a big good luck there.