I live in St. Louis and get these guys going door-to-door a couple of times a year. Usually I do a good job of dodging them entirely, but once in a while, I accidentally answer the door. Usually the word "Vanguard" shuts them up pretty quickly.
Early on when I was more naive, I actually gave one of an Edwards Jones guy my number. Newly married, my husband and I didn't have debt but we also didn't have money either. Anyway, a few weeks later he called me on the phone. "Hey, justajane, I got this great blah-blah-blah, and if you give me 10K, I can blah-blah-blah." It's so long ago I can't remember what he promised, but I just laughed and told him I'd "think about it."
From my vantage point, anyone who is that aggressive is likely a snake oil salesman. If they were worth their salt, they wouldn't need to go door-to-door dressed in their suits in the crippling heat and terrible cold like that.