You're assuming that Korean political/economic system was the same as the one of Europe. It was not.
Nobles didn't own all the lands or people around them. Some of non-noble people owned their own lands, others didn't and had to rent lands from landlords.
So the story that you quoted means that Grandma Jang was generous to poor people who have neither lands nor money to rent lands, and allowed them to work on her lands.
Those who worked not just did the work but also got paid. That's what I assume. I don't really know what the truth was (nobody would know), but the intention of the story is that she provided a "job" to those poor people.
Nobles didn't own all the lands or people around them. Some of non-noble people owned their own lands, others didn't and had to rent lands from landlords.
So the story that you quoted means that Grandma Jang was generous to poor people who have neither lands nor money to rent lands, and allowed them to work on her lands.