Hi Tim,
I know I have heard some awesome sermons from 'tent makers', and I wonder if it's because of the fact that they are in the world...living Christ. I am not down playing study, but I guess sometimes it can come from more than just books. Scripture can be pondered anywhere, and the Holy Spirit can teach us a great deal through our exchanges with others.
Now, these large churches that are putting a lot of responsibility on one man may need to pay him, if they are asking for all of his time. You know, three sermons a week, attendance at various youth nights, board meetings, and prayer meetings, etc. He does have to support a family, and so if there is really no time for an outside position, then they should pay him. A workman's worth his wages, right?
I can see why some prefer to work like Paul so that they remain above reproach, though. The church I attended in St. Louis had two 'tent maker' ministers, and there is some wonderful teaching coming out of that place.
The Lord bless you.