The difference in most towns between a 2 family house and 2 condos is usually just the paperwork that is associated with the deed. A two family deed is simple, just like a single family home, but a condo deed is more complicated, as it explains the relationships between the two owners, with their shared expenses and responsibilities. As Ms. Jones mentioned, an attorney in your area with experience doing this conversion in your target town will be best, in case their are any local ordinances that would make this more difficult than is typical. I would also check with a real estate agent to make sure that you are "moving the property forward", that is, improving it. Usually, this conversion would increase the value of the property, BUT NOT ALWAYS. Not all two families are suited for conversion. So check first! It's a lot of paperwork, and you don't want to do it twice.
The most important first step is to contact a real estate lawyer. This lawyer should be familiar with your town and its requirements and zoning laws. The money you spend will well worth it. And most lawyers will give you an idea of what is involved over the phone.
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