Patrick, there are PLENTY of of old guys still riding. I'm 37 & do light street riding/park riding/racing.
I'm nowhere near close to being pro, or even a good am, but the point is to have fun. Check out some sites like vintagebmx.com, bmxmuseum.com, o-sbmx.com and you'll find a bunch of guys riding at all levels.
To answer your question, a little more info would be good. You planning on racing, hitting the local skateparks, or just cruisin around? What's your budget like? Give us some more info like that & we can point you in a few good directions.