Not really.
First check if the seller is the real owner of the lot being offered for sale.
One way of knowing this is get the Land Title(Original Cetificate of Title the Transfer Certificate of Title) of the lot and check if the seller is the lawful owner of the land, in case the land being offered for sale is a registered property.
If the land is not registered, check the Tax Declaration of the property if it bears the name of the Seller.
If none of the two are present then "caveat emptor" or buyer beware, because you might be ending up empty handed. From your narration I'm of the impression that the land being offered to you is not really owned by the seller and that he is just selling his rights to you. This rights might involve only the sellers right to occupy the property and not its ownership. What if this right has an expiration or if this right willbe terminated by the person who granted the same to your seller? You might just get nothing out of it.
So, check things out first before investing your hard earned money.