It's bad to expect others to pay for your vacations.
Isaac was invited by his friend Amy to go on a trip to Berlin.
Isaac wants to attend the trip.
Isaac accepts Amy's invitation and takes his savings with him to help pay for his way and some gifts.
Isaac accepts Amy's invitation but doesn't take any funds with him.
Amy and Isaac are both able to afford to do everything they wanted.
Amy is left to cover the cost of everything and it causes tension between her and Isaac.