Generally, unless you are buying in bulk you are going to struggle to make money on ebay/amazon selling video games...
If you are looking to sell retail and at market stalls ect then there is money to be made.
For a new release title you are looking at around £26-£27 (PC & PS2) trade price from most of the main wholesalers. I know this because I was in the DVD market for many years and thought about going into video games only to find that there was less margin to be made than dvds..
With regard to finding wholesalers I have a few contacts but the price of £26-£27 a title is fairly complimentary until you are buying 1000's per week of a title.
Hope this helps as a starter,
Anthony