Accounting entry for machinery given on rent for 36 months,

we enter in to rental agreement  with various customers for 36 months, where in we give our machines to customer and get monthly rent, and in our books we show the machinery in assets and claim depreciation.  After 36 months the machinery will be retained by the customer at a cost of Rupee.1/- , as per the rental  agreement , 

1.Are we doing right by taking the machinery in our assets
 

2.What will be accounting entry once the 36 months are over