Let's begin with Mishnah 1 of the tenth chapter of Maseches Pesachim. The Mishnah opens: "Arvei Pesachim samuch le'minchah" - on the eve of Pesach, close to the time of Minchah.
Which Minchah does this mean?
In halachic terms, "Minchah" can be understood in two ways:
Minchah Gedolah: the earliest time at which Minchah may be davened - six and a half proportional hours into the day. On a day when the sun rises at six in the morning and sets at six in the evening, this time falls at twelve thirty.
Minchah Ketanah: nine and a half hours into the day - on such a day, three thirty in the afternoon.
The Gemara explains that our Mishnah is speaking about Minchah Ketanah. "Close to Minchah" means half an hour before that time, that is, nine hours into the day - on a six to six day, three o'clock in the afternoon.
"Lo yochal adam ad shetechshach":
From that hour on, a person may not begin a meal until nightfall, when the time for eating matzah arrives. The Rishonim explain, however, that one may eat a small amount of fruit and other vegetables, as long as he does not fill himself up; the prohibition applies only to an actual meal, once the time of half an hour before Minchah Ketanah has arrived.
"Va'afilu ani she'b'Yisrael lo yochal ad sheyaseiv":
Even a poor man does not sit down to the Seder until he is in a position to recline on his left side, the way we do when eating the matzah and drinking the four cups - the manner of freedom. In ancient times people would recline on couches while eating, and even though a poor man is not accustomed to this, on the night of Pesach he is obligated to recline.
"V'lo yifchasu lo me'arba kosos shel yayin, va'afilu min hatamchui":
Even a poor man may not be given less than four cups of wine; everyone is obligated in the four cups. The Mishnah goes further and says: "Va'afilu min hatamchui" - even a poor man who is supported by the communal food pot.
It is worth noting the levels of poverty:
One supported by the kupah: a person who receives a weekly allowance from the charity collectors.
One supported by the tamchui: a lower level - someone who has nothing to eat even for that day. They would go around the city, collecting food from various people and distributing it to those who had nothing at all.
Even though a person is at this level of poverty, the obligation of the four cups rests upon him, and the charity collector is required to provide them for him. And if for some reason the collector does not do so, the person himself must do whatever he can: even sell an article of his clothing, borrow money, or hire himself out for work, so that he will be able to buy wine for the Seder night.