There is a safe harbor that allows a presumption that you are engaged in for profit if in 3 of 5 consecutive years the activity is profitable.
See https://www.irs.gov/pub/irs-utl/irc183activitiesnotengagedinforprofit.pdf
However, the IRS uses nine factors to distinguish between a hobby or business activity.
See https://www.irs.gov/faqs/small-business-self-employed-other-business/income-expenses/income-expenses
