Complex sentence: The group's official affiliation with the National Black Panther Party member cost three hundred dollars, and didn't occur until April 1971 due to a number of legal problems and harassment by law enforcement agencies.
Split into simpler sentences: The group's official affiliation with the National Black Panther Party member cost three hundred dollars. They did not complete the affiliation until April 1971 due to a number of legal problems and harassment by law enforcement agencies.