Door to door "scammers" in Heights & beyond

GF who lives in the Heights was harassed by a man going door to door purporting to be selling backpacks to benefit children's after school programs in inner-city Houston yesterday. After she told him that she didn't have any money to donate, he refused to leave the doorstep, and even began commenting on her looks and figure. She closed the door and he eventually left. Next day (today) he came back and was knocking on her door. She didn't answer. She lives in a gated townhome division off of a fairly busy street. I've heard stories of these guys going around and casing/scoping out houses. It was also odd that when we went back to review the Ring doorbell footage, he made a point to stand out of the way of its camera.

Has anybody had any experiences with these types of people? Are they mostly harmless? When I lived in Louisiana, I had a guy come to my doorstep purporting to sell magazine subscriptions to benefit inner-city kids, and his schtick was basically verbatim to the guy who was at my gf's door.