Money

Vital Documents
You need vital documents, like a birth certificate, social security card and ID, to have a bank account and file taxes. I replaced vital documents on the street initially with help from homeless services in San Diego. Later, I was able to do it on my own because I had earned income and a mailing address. Once I had those things in place, getting new ID was very similar to how I got it as a middle class American.
Notary Public
Replacing Vital Records
Assistance with Replacement Documents

Banking (and similar):
Bank Accounts

Casual Income:
Casual Income
Recycling Centers: Cash for Trash
Reddit/beermoney
Freelance Tools
A Job You Can Carry in Your Backpack
Half Baked Idea: Panning for Gold

Gift Cards:
Gift Cards
Cash for Gift Cards -- Addendum
Starbuck's and Domino's Rewards and Gift Cards

Taxes:
Taxes
Information Security: A shredder alternative
If You Are Homeless, Cloud Storage is Game Changing

Debts:
Debts
Payday loans
Re-establishing Credit While Homeless

Etc:
Finding Road Money
Pennies, Nickels and Dimes
Money and your Headspace
The California Plastic Bag Ban (and Food Stamp Exception)