What are the documents required for a person to sell the property

RELIGION:HINDU Is it advisable to buy a property from one of the wive's of a deceased person? I was planning to buy a property in bhubaneswar from a widowed lady. One fine day i happened to visit the property on sale.I decided to enquire about the property from the immediate neighbours.I discovered that the rightful owner of the property Late X had two wives the first bieng the lady trying to sell the property.She possess all the documents of the property.She has even applied for a legal heir certificate in the name of her, her son and daughter.Is it enough for me to buy that property after having all property related documents.What if the second wife intervenes after i purchase the property.Will i have be the rightful owner then.Can her(2nd wife having2daughters) case b contested??? What document confirms the ownership of a particular property for a person to sale? Will it be a fraud case by the first wife if at all i buy it?? What should i do taking all the situations into context?