Philanthropic scam in P. G. Wodehouse's "Something Fresh"

Question

In the novel Something Fresh (1915) by P. G. Wodehouse, a scam is mentioned whereby a man advertises in the newspapers proposing to give a sum of money to anyone who cares to apply, provided he is not a minor.

It was the same old game. A Mr. Brian MacNeill, though doing no business with minors, was willing—even anxious—to part with his vast fortune to anyone over the age of twenty-one whose means happened to be a trifle straitened. This good man required no security whatever; nor did his rivals in generosity, the Messrs. Angus Bruce, Duncan Macfarlane, Wallace Mackintosh and Donald MacNab. They, too, showed a curious distaste for dealing with minors; but anyone of maturer years could simply come round to the office and help himself.

My question is, what exactly is the scam and why the prohibition on minors?

Answer 1

From this site, I found speculation that this is reference to predatory money lending and not philanthropy as you originally guessed.

Brian MacNeill, Angus Bruce, Duncan Macfarlane, Wallace Mackintosh, and Donald MacNab are all typically Scottish names. It may be that Wodehouse is merely alluding to the traditional stereotype of the tight-fisted Scot. Another (unconfirmed) suggestion is that the laws relating to money-lending were different in England and Scotland at that time and that English money-lenders found it advantageous to establish a place of business in Scotland and to masquerade as Scots.

Such advertisements on behalf of money were at one time so common that for several weeks in January 1914 The Times carried a message on its front page stating that “the greatest possible care is taken to ensure that all advertisements inserted are trustworthy . . . Moneylenders’ announcements are rigorously excluded.”