Keep very complete records of everything you earn and records of any expenses you have.
If you just started working in September 2019 you will file your first tax return in 2020, sometime before April 15, 2020 for the 2019 tax year.
Since your earnings will be reported on a 1099Misc that means no taxes or Social Security or Medicare are being withheld from your pay, and you will be paying Self-Employment tax for the SS and Medicare, as well as ordinary income tax. The Self-Employment tax for SS and Medicare is 15.3% of your earnings. Your "ordinary" income tax will depend on how much you earn as well as some other factors.
https://ttlc.intuit.com/questions/2893577-does-a-1099-misc-mean-i-m-self-employed
https://ttlc.intuit.com/questions/2902389-why-am-i-paying-self-employment-tax
https://ttlc.intuit.com/questions/1901110-do-i-need-to-make-estimated-tax-payments-to-the-irs
https://ttlc.intuit.com/questions/2903027-how-do-i-report-income-from-self-employment
https://ttlc.intuit.com/questions/3398950-what-self-employed-expenses-can-i-deduct
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
