People who invest in theatre productions are called Angels. This is probably because, like guardian angels, quite often there's not much return on your investment, except the knowledge that you have contributed to the greater well-being of mankind. But it does give you the opportunity to become involved, and like all hobbies, it can be worth it for that alone.
Let's start with the drawbacks - remember that the curtain can go down as well as up. Of every five West End shows, three are flops, one breaks even, and one makes a profit. A sobering thought, but better odds than the National Lottery and a lot more fun to play.