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In my view, yes, for two flat properties. And like @aggi says, if you get on well with the other live in share, it will be good, and in that case a share might be desirable. They can move, though, and if you veto anything, things can turn sour quick. And from what you say about your neighbour, it sounds bad. Anything else is different, because in a three flat property and a live in freeholder the other two leaseholders can force a share.
So in order of desirability: