In response to Tims question I can only back up what Max has said, Time is the main thing, I spend on average 8/10 hours a day sorting out stuff for the VTC, sometimes longer. You'll take ages just getting a few drivers and it will seem very tiresome, I think Swift has the biggest following though I know of another that has over a 100 drivers.
Your always striving to get the best results for your drivers, alot of VTC's are done by dedicated people who want to share their joy of the game, and for this reason they put the effort in.
Finance wise, well you have the cost of servers and website stuff, as well as any licences you use. However a few VTCS avoid these costs by using social media, but contribute enormously to sites similiar to this one.
Understanding your drivers is always good BUT only providing/ allowing mods to better enhance the gameplay not just xp and cash.
Hope that helps Tim please feel free to pm me with any questions. Good luck with it.