The separate entrance, bathroom, and kitchen would usually make it a separate unit. However, the 'shared' area may be able to get you out of that. Can you access the other 'unit' without going outside? If so, I would not worry about the issues for a separate unit (which are a bit of a gray area anyways).
Again,, the conversion to personal use has not affect on your taxes (besides stopping depreciation), so the timing of that is not imporatant from that viewpoint. However, in case it were to be questioned about being a separate unit, I would recommend converting to personal use (as part of your Main Home) at least 2 years before it is sold.
