It would be interesting as a study to go through and calculate how much more a poor person pays per year for the same level of service just because they're poor (e.g. higher car payments, no 0% APR offers, account fees, etc).
http://www.nytimes.com/2014/09/21/your-money/in-checking-acc...
Not sure if it's paywalled, so the gist is that for relatively affluent folks, the annual cost of a checking account is ~$18. For the "cash-strapped" it's closer to $500.
Obviously that's just checking accounts, but I wouldn't be surprised to learn that many other things are more expensive for the poor as well.
How it doesn't violate usury laws to charge someone $35 for a $5 overdraft, I'll never understand.
Do not pay for a checking account, ever. If your bank is charging you a fee for your account, call them and say "I can get a free checking account at X competitor, I am going to switch to them unless you can match that."
Hell, Charles Schwab offers a free checking account and will refund ALL ATM fees every month.