For the French this is highly normal. Often the guest will offer to pay the next time. Je t'invite la prochaine fois . You will almost never see French people dividing up a bill at the table. So be forewarned.
Money still has a vulgar connotation.
If you're invited to someone's house in the evening, it's almost always going to be for dinner, unless it has been clearly stated otherwise. But don't show up empty-handed. As the economy weakens and people are more conscious of their budgets, more and more groups of friends are adopting the collective dinner or pot luck concept, but if you're not sure of the folks don't suggest such a thing to start. Dress slightly better than you think is appropriate. The French, even young people and students, tend to dress well when going out socially.