Hi! I'm starting a copy writing side hustle that is currently projected to make about $1000 by the end of the year at a minimum. Right now, I'm paid through Venmo and have not yet established a legal business entity.
Speaking in general terms, you'll need to file for your business if your net earnings (income minus expenses) from self-employment were $400. or more. Depending on how you organize your business (sole proprietor, single-member LLC) and what state you live in will determine what, if any, state reporting requirements you would have. I'm not quite certain what you mean by payment apps having an impact on your taxes. You'll need to be a little more specific.
As far as receiving a Form 1099-K, please see the following link for information, including what qualifies you to receive a Form 1099-K: