I found this video explaining how to mod the game to get unlimited backpack storage, money and eridium.
Basically you need to download CheatEngine and grab a cheat table for borderlands 2. I recommend only doing the inventory edit so you wont feel like destroying the entire game experience and being a complete cheater.
This just smacks of the video and website creator posting here to get hits. It's kind of pointless anyway. Money is just used for slots for eridium since you'll find better weapons than you can buy. And inventory isn't that bad once you realize that money isn't that useful and you can just stick to picking up greens and higher.
Money and Eridium are pointless, but getting enough bank slots to simply freaking STORE one of each of the legendary items is actually kinda nice. I hate having to dance around characters to give people things.
Once again snatching defeat, From the jaws of victory.