It seems to me that there are two bits of folklore here:
1. Traveling men (bums in general; Gypsies, traveling salesmen, soldiers, & sailors in particular) have been around and are better at satisfying women sexually than homebodies are.
2. If you are hospitable to a traveling man, making him at home in your house or your body, he may turn out to be rich, or an angel (like the ones in Sodom), or an outlaw (Pretty Boy Floyd), and then you will be rewarded for your charity. Of course, he more likely will turn out not to be, but never mind; this is a very old & charming kind of propaganda.