I went to one of those once. The free event is 10% information, 90% sales pitch for a $200 (I think) class. I read online that the $200 class is apparently a sales pitch for a $15,000 class.
If you know nothing (and are very, very good at resisting sales pitches!!!!!!!!!!!!!!) the free class might be worth going to. Otherwise, just read stuff on biggerpockets.com instead.
(See that bit in bold? Read it again, because I can't stress it enough! I'm nigh-impervious to sales pitches and even I signed up for the $200 class at the end, only coming to my senses and canceling the next day. Actually, that reminds me: that free class is "okay" if you want to learn about real estate, but excellent if you want to study salesmanship techniques.)