You (or, at 18, your parents) probably have one or two friends who are notaries. Most banks have some on staff and they're usually willing to notarize other, non-bank-related stuff for account-holders too.
I meant those as helpful suggestions but...ummm...thanks for the reminder. Also, you'd be surprised who is a notary. It's not all high-end finance people. I know one who works as a receptionist at a car dealership.
Earlier this year I needed to get something notarized. Went to the UPS store 3 blocks from my work, paid $5 per signature (=$10), walked out 5 minutes later. It's a hassle, but for a $500 transaction it really isn't such a big deal.