No, there's no limit. You report all the income you earned as a self-employed individual.
There is a certain
amount you have to make before you are issued (or issue) a 1099-K form
however. You must have made at least $20,000 or more before any 1099-K form is
issued to you.
As a driver for Uber, you should receive a 1099-K but only if the income earned was over the reporting limits for those forms...which is $20,000 for the 1099-K. However, just because you didn't reach those levels, you still must report that income to the IRS. The cost of the upgrade can be written off next year as a business expense.