This thing called ...what?

A neighbor came to me this morning. He is a farmer. He farms rice. Not really a friend, nor enemy but I knew him for he was once my hired hand years ago. I was wondering what he wanted from me but anyway, he finally came to it after some weather talks. He needed to buy 4 bags of fertilizer for his rice farm and was asking if I could supply the fertilizer for him. In return, he said, he'll pay me with 3.5 sacks of rice per bag of fertilizer. Hhhmmm..tempting..that means 14 sacks of rice in 2.5 months! But of course I can't say yes for 2 reasons. Mainly because I can't afford it and also because I can't allow myself to take advantage of the poor farmer in this situation.