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Is d land sloppy??if not try to leave a gap inbetween ur fence and ur neighbours so as 2 create an artificial drainage..wish u all d best of luck

First, you will need to find out why your prospective neighbor built his land so high.I'm suspecting the area is low lying or water prone. I can't deduce this from your picture. If this is the case, you will need to make up your land I.e. fill it to at least the level of your neighbor's before building. That might not be cheap. It is all a relative thing, water will flow from a higher point to a lower point. As per the drain, you will have to make a gutter parallel to the fence to allow the water drain out.
On the bright side, you will be sharing a well constructed fence - 1 down out of 4!

Thanks guys, I think they have packed sand from the land over the years that's why that part is like that, as for the water from my neighbor I have the right to block it according to people, all we will have to do is to come together and do gutter together, the place is a close of about 6 houses, all I just need to find out now is to know why he did his floor so high and if water will be flowing to that part of the street, so I will know how t fix the prob before building will commence