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.

How much tax will it cost for importing if I am buying an items outside India?

i am planning to go for an internet shopping and i would like to know how much tax will it cost me again for import the items to india and I am trying to shopped from some US sites means items will be shipped from US?
i am planning to go for an internet shopping and i would like to know how much tax will it cost me again for import the items to india and I am trying to shopped from some US sites means items will be shipped from US? Items will be like clothing items thirts,caps,necklaces etc…
is it includes in the shipping cost or i have to pay an additional amount again