So... not sure if this is a really stupid idea, but we need to upsize and build a house, but are hoping to join it to our existing (currently separate)…

We build a lovely granny flat in our back yard. Now we are looking to knock down and rebuild the main house, and the granny flat might be in the…

Thanks folks, that's very helpful!
Old bloke - I totally forgot about changeover costs - thanks for that!
We are in the area we want but on a busy road - but…

I assume this is on par with "how long is a piece of string", but I just don't know where to start.
Basically, DH and I are at the point…