[BirdOPrey5]

At the forums I visit that have a paid administrator it's usually an internal side job of someone who has another job in the same company like a sales rep or such. Most forums being an admin would not be a full time job.

That said they all do some moderating as well, that can be a valid role.

If you were hiring just a part time admin though to do what you said it shouldn't depend on the number of members or posts- although a bigger forum will take a little longer to backup then a small forum, for the most part time to upgrade, debug, ans customize is independent of forum size.

The version of vBulletin would not have any direct affect on pay, though with more options in VB4 (assuming you own the Suite) there is potential for needing to put in more hours.