Most people would charge, I don't know of anyone that would do it for free to help out unless there was a trade.
You're from the latest generation of users on this forum, but before you, believe it or not, everybody helped eachother out for free. It was called the vBulletin.org community. Users shared their resources, worked as a team on an addon, and helped eachother with questions and installations or things, or at least walked them through it. Assuming there's a charge now is what I think is the wrong approach perhaps. Back in the day when someone did offer these paid services, it was not done through this site, but through their own personal web site, so everybody felt welcome and brave enough to ask for help such as bob did.