I will follow what other people are saying, rent.
If you have never snowboarded do the following
Goto Big Bear - Pay them 90 dollars for an all mountain pass, 2 hour lesson, and rentals.
Honestly i wouldnt even bother with the all mountain one if you have never gone..you can get the beginner area + lesson + rentals for 80.
You cant do squat with 100 dollars. Rentals are only 20 dollars if you do it this way, plus you get lessons, dont waste your time trying to have your friends teach you. They wont want to spend all day teaching you when they paid 60 dollars for a lift ticket.
Pretty much any resort worth going to is going to have some sort of beginner package that includes Lift Ticket + Rentals + Lessons for a discounted price. For example out here at Mt Hood Meadows they have a killer 3 pack deal. 3 days of rentals, 3 days of lessons, 2 days of bunny hill lift ticket, 1 all mountain lift ticket for 99 dollars. Which is just a retarded deal...considering 1 all mountain ticket alone is 60 dollars. Its like 400 dollar value lol...it looks like Big Bear has some stuff similar
You get a free 20 dollar voucher with it too...so your second lesson you basically dont pay for rentals.
You need board + boots + bindings..for 100 bucks no way...even used will be tough.