If you charge proper rates, you will often get referrals from other pros and even suppliers.
Charging "hobbyist rates"? You'll get treated like one, by suppliers as well as your local peers. There's actually nothing at all wrong with that, as long as we remember that it dosen't usually work both ways.
Also remember that if you exceed a sideline income threshold, you're open for business in the eyes of the IRS and local tax authorities, whether you want to admit it or not. The IRS doesn't really care if it's your full-time gig or not. The good news is that stuff you would have bought for your hobby now becomes deductible against the income it brings in. Have a really bad year in between some really good ones? Small business losses can actually reduce your "day gig" tax burden.
A few hours with a good local CPA can be a great value if you really want to make a go of it. He or she can help you get properly set up, get a simple accounting system going (like Quickbooks), and sleep better at night.
Have fun!