legal advice on buying a property?

we r planning to buy a semi-independent house from a real estate builder.
the case is
1. the owner of the land has given “power of attorney ” to the builder and has not sold the land to builder.
2. we do not know if the owner of the land is alive or not and we r trying to contact her.
3. builder says he will produce latest( date if which is unknown) power of attorney documents.

my doubt is :
in this case can i proceed to buy the house? in future can the owner’s children file a case against this property and claim it to be theirs as the owner has not sold to the property but only given “power of attorney ” to the builder?
also the owner will not be present during registration, it will be the builder who will sign when we register the property.