Certain transactions come under suspicion if they do not appear to be on par with the same transactions for the same type of deal.  In other words,  if a house is worth say $200,000 and it is transferred for $10 that transaction seems not to be legitimate in its own right.  It is known as "consideration" for the transfer of the deed and the ownership rights.  Consideration is the inducement to a contract.  If the inducement is really NOT inducement then the transaction looks suspicious.  It has to be fair.  So if the amount is low sometimes it is written "plus other considerations" like say, a life estate or something else that is of value.