Student or Learner
''The article is about lawyers, who are very eager when it comes to earning money.''
is it correct to use ''who'' when referring to a group of people? should I use ''that'' instead?
One other thing: watch that comma!
"lawyers, who" ("non-restrictive": the article is about lawyers in general; and, by the way, all lawyers are eager about money).
"lawyers who" ("restrictive": the article is about those lawyers who are eager about money, not necessarily about all lawyers in general). In the restrictive sense it is traditional to use "that" (and no comma) rather than "which", but in practice the "who" is quite acceptable for people, and probably BETTER for groups of people.