Baseball card collection for 400 bucks...?

This collection had tons of auto base with COA s and good rookie cards that look like they'll be some money one day and i know its worth atleast double that ampount but was this a good idea for me b/c I'm trying to invest a little to gain a little but is thisa smart move for me or not b/c I still have time to change my mind..Help me and tahnks a bucnh and I plan on selling these in the future if I buy! I only getting rookies and auto baesball cards and that are sign by Tori Hunter and some other stars but nio many of them but the cards are at good valuse and shape b/c they coming from a old card dealer who was looking for some quick money and I did'nt screw him obver but i just felt like this is agreat oopruntunity to make someney or was it?