for your budget, i think you can commission those metal workshop to build one for you. plenty of drawings and plans on the net. just google for it.
Hmm $500 for track abit impossible, even if second hand.
few years back bought a set for like 6-7k and that was like a budget one...
Rent from Film Equipment Gallery or something if u need once awhile.
Wow bro, u use it for weddings? Must be multi cam wedding to setup hor?