Not land,until he has been a resident of Poland for2 or 3 years
You're wrong about that. If his spouse is Polish and they have the usual common property arrangement, it's enough for one half of the couple to satisfy the requirements.
I would stay away from rolna land,a mess with regulations.
It's not really that complicated. You wouldn't want the hassle because living a healthier, self-sufficient lifestyle on a small holding, with a veggie garden and hens etc is not your goal. But that's what the OP wants so for him the extra bother may be worth it.
the buyer is obliged to conduct agricultural activities on the property being purchased.
It doesn't have to be anything very arduous though. What you do at your summer house with the veggies etc would be enough or keep a couple of goats, a pig, a few ducks or geese and Bob's your uncle :))