Retirement Gift for my parents

My Dad is about to retire and I have been trying to get him and my mother a gift. My idea is to buy for them a piece of land and build a three bedroom house for them with a backyard garden for their fresh vegetables.

I have identified a piece of land and even paid for it's booking and I wish to raise enough funds to pay for it and build for them a beautiful home they will love and enjoy. Whatever amount is left after building I will buy for dad a car or a pickup that he can use to run whatever business he will choose to do, and for my mum I will help her in setting up a farm for business because she loves farming.

I saw the excitement and the joy it brought my dad when, after identifying and booking the piece of land, I took him for site seeing and he loved it. He could not stop talking about it all the way back home and I felt I needed to do more than just getting the piece of land. My desire has always been to one day give back to them for their sacrifices though it might not be equal to what the have done for me and my siblings but it will be something.