The middle ages last roughly from the fall of Rome to the fall of Byzantium-- that's a thousand years, and the area we usually mean stretches from Iceland to the Middle East, from Spain to Kiev. So it's a lot of different places and a lot of different times.

What kinds of swords would be used -- if swords were used at all-- and by whom would be a question of where and when you're talking about. "Lower class" also is vague: there's slavery in many places and times-- the answer to "what kind of swords do slaves carry?" is "none".

Very generally, the peasantry, if armed, would be more likely to carry some kind of improvised spear than a sword. Swords weren't cheap, and they took some skill to use effectively. In Wat Tyler's rebellion (1381 in England), we're told that the rebels were armed with "sticks, battle axes, old swords and bows"-- eg "whatever they could get their hands on"

So if you're trying to be accurate, you'll want to specify where and when you're writing about: is this Ireland in the year 900? Or Jerusalem in the year 1100? Pick a time and place and you can start to fill in details . . .