If you want to get in with builders, you will do better by meeting the superintendent. If they are very loyal that is a plus and a minus. In my opinion you need to try to be his emergancy work guy, if he needs something done right now, you need to be able to get it done. It may be something small like a remulch for a new buyer or a foundation dig for a water problem.
If you really want to work for builders, you need to make sure your aware of the pitfalls. There are a lot of builders going bankrupt or letting their vendors carry their debt. Check with other subcontractors to see if they get paid in a timely manner. Some builders want to pay when the house sells and the longer it sits on the market, the less profit they will have to pay the bills.
Builders can be a great source of work or a huge burden for you. We have had both.