Was President Obama a paid lecturer at Chicago Law School?

Absolutely. In fact, he was an adjunct professor there for twelve years (some sources say "lecturer," some say "adjunct professor"-- different schools use different terminology to describe those faculty members who are not employed there full-time); he was sufficiently well-respected that the university's dean has stated in print that the university offered him a full-time job as a professor, but he decided he wanted to go into politics instead.