They were not wealthy and therefore charged admission to the public to see the angel. This enabled them to afford a better lifestyle, a miracle to some on it own. The attitude of the author and characters is one of complete nonchalance. This attitude is conveyed to the reader and makes the events much more acceptable. The author, by making the story so short, gives the reader no time to question the events taking place.
Any piece is open to many different interpretations.
Some will look only at what is on the pages of text and never consider what is written between the lines. The old man could indeed be an angel. However, when one considers his progress through the story, it seems to be that the angel is newly found in his position as an angel. One could also conclude that the angel is aging backwards. Instead of beginning as a child who knows very little and learns more as he grows older physically, the angel finds himself learning more and becoming younger physically.