After you file

Since you did not receive a 1099 you will enter your income as "Other self-employed income".  You will also want to be sure to report all the expenses you can to reduce your income and your tax liability.

To enter the income you will follow these steps:

1. Open or continue your return in TurboTax
2. Search for Schedule C and select the Jump to link at the top of the search results
3. Answer Yes on the Did you have any self-employment income or expenses? screen
4. Answer the questions on the following screens until you arrive at Let's enter the income for your work
5. Select Other self-employed income and Continue
6. On the next page you will enter your income (you can just describe it as "Cash" since there's no 1099 to tie it to)

Then check What self-employed expenses can I deduct? for ideas on valid expenses to deduct.