I'll admit up front, it has been quite some time since I looked at the rules for sale of personal residence.
Having said that, there may be some exemptions I'm missing. But, if you move out, live in another place as your principal residence, and rent out the other side; unless there is some exception, I would presume when you sell it, it would no longer be considered a sale of your principal residence.
I'm not sure of the result if you just left your side empty, pending the sale. Without further research, that to me would be a stronger case of selling a principal residence, then if it was converted to rental and actually rented out, depreciation claimed, etc.
That's why I'm putting this as a comment, and not an answer. Hopefully someone with more expertise in this area will answer.
**Disclaimer: Effort has been made to offer correct information; but due to the discussion forum limitations, the poster disclaims any legal responsibility for the accuracy of the poster's response**
