I bought the car pass and wanted to go buy some dlc cars but it still wants me to pay money for the DLC.
Which DLC where you trying to buy, and where were you trying to “buy” them from - the marketplace, or the in-game Autoshow? It’s possible what you wanted wasn’t covered in the Car Pass, which entitles you to the first 6 monthly car packs. Read here:
http://forums.forza.net/turn10_postsm183093_FH2-Cars-and-DLC-List.aspx#post_183093