I'd consider that a pretty lucky find, especially if your friend recently signed the contract and is a non-Pole.
Signed last week and he's British. It's a fairly good deal but it's not a killer deal (it's maybe 100 or 200zl below the market rate).
You really need to talk to a lawyer who is familiar with Polish residential visas. There are plenty in Chicago.
Very sound advice. Although a relocation company might be a better choice than a lawyer.
Citizenship is definitely worth considering.
If he's retirement age and the claim is from his grandparents, getting citizenship would be a long and difficult process (if it is even possible).