From the examples you uploaded, the resolution/quality doesn't seem to be very good, nor does the colour. Did you use a filter? Were they taken with a smartphone and an Instagram filter used? If so, it's best not to use filters of any sort. The buyer can add their own effect.
Have a read of this from Adobe about how to create better photos:
Blow your image up to 200%+. You have artifacts, halos and noise in the sky. The sky is also oversaturated in blue. The buildings are under exposed.