Pay by cash membership?

umm, ya my parents won't let me buy members anymore. So i was looking for a way around this and lo and behold, pay by cash... It sounded far too good to be true. A fricken 2 year old could send cash in and the parents wouldn't know diddly. Is it really this good? Is there any risk is this? Any possible way parents could find out? If i get busted it bad lol. Thanks for all the help.