Does anyone have any knowledge about opening an online ticket broker site?
To make it very basic, you build the site, list the tickets you have for sale, (or can get to onsell) and depending on ow much people want to buy the tickets, you can determine the level or fee or price you charge for the tickets.
Not sure where you are, but some states have regulations around ticket selling and pricing, so be sure to get knowledge on where you are operating.
One last note, build a good site, but don't put your entire budget into the site, put as much as you can into Search Engine Optimization. No use building a great site that no-one sees.