I am a bit confused because my first idea of a poor person is a person who can't find a job, not a person who has two jobs

I've spent a fair amount of time volunteering in fairly poor communities, and i my experience, many of the people living in those areas work multiple part-time jobs, some "official" some under-the-table.

In the US at least, statistics bare this out- even 45% of homeless people have worked a job in the last week (much fewer have regular jobs, because of the nature of homelessness). 13% have regular jobs (are working poor). ~25% or so of people below the poverty line are working poor, and the fraction has been increasing. I imagine if you include under-the-table jobs, its much higher.