Jet...the problem with your idea is that I can't build a normal house on a half a block and be inside my boundary lines restrictions. The reason for building the duplex is that the land gets divided down the middle and i'd get more space.
Yak_chat...
Obviously I would not go into partnership with someone who didn't have the money. That would be one of the first things I'd sort out to make sure they can afford it and are serious.
Anyway, like I said it's just a thought at this stage. Given the right person or couple, I'm sure it could be pulled off.