sense and sensibility - question concerning the talk between Elinor and John chapt 41

[Alienor]

Hello, I'm reading sense and sensibility at the moment and I don't understand the part when John talks to Elinor about Colonel Brandon giving Edward a living and says this in chapter 41:"Very well—and for the next presentation to a living of that value—supposing the late incumbent to have been old and sickly, and likely to vacate it soon—he might have got I dare say—fourteen hundred pounds. And how came he not to have settled that matter before this person's death?—NOW indeed it would be too late to sell it, but a man of Colonel Brandon's sense!—I wonder he should be so improvident in a point of such common, such natural, concern!—Well, I am convinced that there is a vast deal of inconsistency in almost every human character. I suppose, however—on recollection—that the case may probably be THIS. Edward is only to hold the living till the person to whom the Colonel has really sold the presentation, is old enough to take it.—Aye, aye, that is the fact, depend upon it."
Why would it have been wise in John's opinion to have sold the "living" before the late incumbent died? It's not Colonel Brandon who will pay Edward when he has taken the benefice or is it? I thought the living would be paid by the all the people who live around that vicarage. So Colonel Brandon shouldn't care about presenting any living, should he? Please explain it to me! I'm confused