You can be paying a mortgage on a house worth 100,000 dollars, have a dead-end job, live paycheck to paycheck, with no more than 1000 dollars in savings, and still count as a net-worth millionaire.
Net worth is assets minus liabilities.
If you had no savings or investments and a $100,000 house with a $99,000 mortgage your net worth would be $1,000, not a million dollars.