I would give it 5 years and not 15..How much is the land going for per acre?If price is right, go for it. I would think that within 5 or six years, you will reap beautifully.
Why am I saying this? I bought some 3 (50x100) plots some three years ago directly opposite the KBC station and touching the barabara for 85k, and forgot about them. Was there recently and same is going for 350k. I think that is not bad.
Just for Information, a 40x80 some 2.5 kilometres at KBC, off Kangundo road ARE GOING FOR ABOUT 120K.
aLL THE BEST.