Money found on sold property

Hi, If someone purchases a house from someone else and the person selling the house says I will take some of the things in the house with me (for example the seller took some furniture with them) but told the buyer that all the rest that is left in the house the buyer can have and then the buyer finds some money in the house. Who has a right to this money? It is unlikely that the seller knew everything that they left in the house (as they left old books and pots and pans etc) and assumedly would not have know about the money. Thank you

From what you describe it seems that there is a well grounded assumption that the seller meant to leave behind only the remaining movables but not cash (unless it's a paltry sum which most people wouldn't care for) as it is unusual for people to leave behind cash which is legal tender. This is similar to a man who sells a courtyard which includes the courtyard houses, and when he says to the purchaser "I sell it and all its contents", all is included in the sale, also movables, except wheat and barley which is food for one's sustenance, and one normally takes it along with him. Therefore the money belongs to the seller. (Mishnah Bava Batra 67a, and Rashbam ibid. Shulchan Aruch Choshen Mishpat 215,1 and Sema 5).