"We are unable to locate the page you requested.
The page may have moved or may no longer be available"
Hmmm.....
To try and answer your question, I think the "no tax" limit is less than $10K income per year. What would you call "poor"? Less than $20K? They would still pay taxes if over $10K (in a much, much lower bracket.)
Even if make more than $20K, start taking personal exemptions and standard deductions