I just recently started a job that uses a 1099 form while I also have a job that uses a W-2. The 1099 job has told me that everything that I spend for that work is a write off such as food, water, phone bills, repairs and more. He did not go in depth with the write offs and I was wondering what exactly can I use for a write-off and do I need to file quarterly or just at the end of the year?
If you are receiving a Form 1099-MISC reporting your income, then the company that is paying you is treating you like an independent contractor. In the eyes of the IRS, you are self-employed. Your income from the Form 1099-MISC and any related expenses will be reported on Schedule C.
Since you stated that you also have a job as a W-2 employee, you may not need to make estimated payments to cover your self-employment tax and additional income tax. You could increase your tax withholding from your W-2 instead.
Since you just started the job recently, these changes will take place for your 2020 tax return and that gives you some time to research and figure out what you need to keep track of and report next year.
Here are some TurboTax articles that may help you get started:
What's different now that I'm self-employed?
What self-employed expenses can I deduct?
Self-Employment Taxes Tax Tips -- this one contains links to many different article that may be helpful
The person telling you everything is a "write off" may be exaggerating somewhat. Did he also mention to you that you will be paying self-employment tax for Social Security and Medicare, since it is not being withheld from your pay? And that he is not withholding any federal or state tax--so you have to pay it all?
https://ttlc.intuit.com/community/self-employed/help/what-is-the-self-employment-tax/00/25922
https://ttlc.intuit.com/questions/2902389-why-am-i-paying-self-employment-tax
HOW/WHERE TO ENTER A 1099Misc
https://ttlc.intuit.com/questions/2893392-where-do-i-enter-a-1099-misc
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
https://ttlc.intuit.com/questions/1901340-where-do-i-enter-schedule-c
https://ttlc.intuit.com/questions/1901110-do-i-need-to-make-estimated-tax-payments-to-the-irs