We should always be careful when buying agricultural land. Even government afteracqusition is challenged and at leasttwo tiems courts giveb escalation..
in 1/rd of cases, some ghost springs out from that land claiming to be a heir of ancenstral property and then negotiates unless you area bahubali like mayawati or some thakur.
Did you advertsie in popular new paper ciruclated in that area before buying, about that land and your intention to buy/sell?
If it is ancenstral property , all the ghosts will come alive. A person can claim only when he comes to know. Basically it is mistake of seller and not buyer. But if sales is declared null and void then you are in trouble as seller would have swallowed money by now and you are not likely to get any thing back by civil suit unless he is well settled gentleman. Better to consult a local advocate speciallising in property/civil law. Exact nature of his claim is not nown here.