Purchasing Property from a POA Holder

I am looking for buying a property from a person who has been given power of attorney by the Owner. I have been informed that POA is registered. In Rajasthan, POA when given to a person (not a family member) for consideration and authorizing the attorney to sell any immovable property, then Stamp Duty is 5% and Registration Fee is 1% of the 'consideration'. This Stamp Duty and RF is same in case of a normal Conveyance Deed and the %age is taken on the 'Market Value'. In case of POA given without consideration, Stamp Duty is 2% of the 'market value' and RF is 1% max. 10,000/-. I have some general questions: 1. What is the difference between 'consideration' and 'market value' in this context? 2. What difference does it create if POA is 'with consideration' and 'without consideration'? 3. Why will the person (the POA holder) preferred to purchase 'the property usage and selling rights' by getting POA instead of getting a Sale Deed, even if the SD and RF are same in both cases? I see many properties advertised to be sold on 'POA', why do they do this? 4. If consideration is paid and the POA is registered by paying SD and RF, is it not equivalent to a Conveyance Deed and does not the POA holder becomes the owner himself? The POA has already become irrevocable as the interest is involved. 2. What if the owner dies, in a case, before the POA holder sells the property on the name of the owner ---> Will the power given by owner to someone to sell the property 'without consideration' become VOID? If POA holder has paid consideration, will this POA also become void? Or the POA holder can sell the property even after the death of the owner? 3. Can POA holder sell property on his own name, not on behalf of owner, if the POA is registered as per rules? 4. How to know if a similar POA has not been granted to other persons by the owner? Does any such POA affect the ownership of the buyer in future? 5. If the earlier Sale Deed of the house contains the name of Owner only, and the POA is executed by the Owner himself, can the family (wife, sons, daughters, other relatives) of the Owner claim the rights on the property after or before the death of the Owner, even if such POA where consideration is taken and it is registered as per law? 6. Can the Owner sell the property even without the knowledge of the POA holder in this case, where the owner has already taken consideration and the POA is registered? I shall be really thankful for your guidance.