If you hear a buzz on a stringed instrument, it is usually because something is loose. Pluck the string and use your eyes and ears to locate it. You can confirm the issue by pressing the moving object gently. The sound of the buzz will change as you dampen it with your finger, and you don't have to end the sound to confirm where it's at.
If you can't immediately locate the buzz, the first places to closely inspect are near the string - is it hitting the fingerboard or frets? Is the winding on the string all connected to the string? Next, check the string termini - are the bridge/bridge-pegs and nut moving at all? After that, move to the peg box/headstock. A string on the headstock that's managed incorrectly can definitely buzz. If your instrument was hollow (guessing you have a solid-body electric), you would check the seams on the body for gaps. Still, check where the fret-board connects to the body and any other connections between the parts of the guitar's body. If it is an electric and you haven't found it yet, swap cords, amps, pedals, etc... until you isolate what is causing the buzz. Remember that the connector (i.e. the 1/4" plug) can be a problem, but modern electronic components mostly buzz on purpose if at all.
If you do a good job at all of this, you have a good chance at not needing to pay a shop, but if you end up needing to re-glue part of your instrument or can't find the issue, the luthier knows best.