Here's a point no one has touched on. If you are doing a house concert under the auspices of a not-for-profit org or club, then you need to make a record of the amount of money made from admissions. You also need to make a list of expenses - what amounts were spent on what. Your club treasurer, who has to write a report every year showing what money came in and demonstrating that it was spent on legitimate club expenses, will thank you.