You only have to look at Google maps to realise that Nairobi is one of the few cities in the world with alot of 'available uninhabited' land near it. Cities such as New York, Los Angeles, London, Monaco etc don't have that luxury. So focus your eyes on the great plains on southern parts of the city..... Kitengela, athi river, ruai, kamulu etc. Am sure 1.5m can get you land there. Otherwise in the already developed north prices are 22m per half acre. Even in Githurai a 40x80 is going for 6m.