Rehab into 2 family or condo conversion

I am analyzing a potential deal where I can flip a 2 family in Massachusetts.  I am trying to decide what the better move is--flipping and keeping it as a 2 family or doing a condo conversion.  I think that the condo conversion has a better upside and will fetch more $ in the end.  My question is, what stops me from doing the condo conversion and listing the property as BOTH a 2 family investment property AND 2 separate condo's?   Ultimately the underlying concern or question is if a condo is created, does it need to be used/sold as such?  

Also, what are the costs to consider when doing condo conversions?  I am not looking for $ amounts, but rather specific concerns to be focused on.  The only variable that I can think of that would be different then just rehabbing as a standard 2 family is the associated attorney fees for creating the condo docs (master deed, etc).