Non Warrantable means that the condos do not meet the requirements to be sold to Fannie Mae or Freddie Mac.
A condo questionnaire is used to determine whether the criteria is met. There are MANY requirements but in this particular case if only 16 out of a proposed 200 units have been built and sold then that alone may be reason enough for this project to by Non Warrantable.
Non Warrantable condos can be quite difficult to finance although some lenders may be able to help you. You say you would be selling in 4-5 years. What if the original plans for the community are never completed? What if the HOA dues increase substantially or there are significant special assessments? What if the community is still Non Warrantable in 4 or 5 years when you are ready to sell? The developer could still be under pricing resales for years to come. So many variables to consider. Good Luck!