A neighbor's retirement is a big milestone. You want to celebrate them properly, but the costs for food, decorations, and invites can sneak up on you.
The key is timing. You need to start booking things three weeks out to get the best prices, but you can spread the cost out if you plan your math early.
Just remember that the intro period is a deadline, not free money. If you haven't paid the full balance by the end of the 18 months, you'll start owing interest on what's left.