بسم الله الرحمن الرحيم
In the above mentioned case, if you buy the said plot in 17 lakh rupees in instalments then it is lawful for you and it is not interest. It is lawful to sell and purchase anything on less price in case of cash and on high price in case of debt (instalments) provided the condition of cash or debt is cleared and the dealing is done accordingly.
ألا يرى أنه يزاد فى الثمن لأجل الأجل الخ (هدايه)
Allah knows Best!
Darul Uloom Deoband