There are ways to get into the Masters, but it is very hard to get inside the ropes, even as a caddie. Atlanta lawyer Richard Grice is caddying this week for US Amateur champion. Last year the Atlanta Athletic Club hosted the US Am and a group of members offered to caddie for players who did not have caddies. Grice agreed to caddie for Gunn Yang. During the course of the event, Yang offered to pay Grice. Grice said he did not want to be paid, but if Yang he won, he wanted to caddie for him in the Masters.
Yang came into the event as the 776th ranked amateur in the world. Grice figured he would only have to caddie for a few days. It tuned into a marathon caddying job and lead to the US Am finals.
Yang went on to win the US Amateur and was rewarded with an invitation to the Masters. Grice is now skipping some work to caddie at the Masters.
A more detailed story is found here: http://www.wsbradio.com/news/news/walk-lifetime-atlanta-lawyer-turns-caddie-masters/nkqW9/