Can a condo association President vote for unbuilt units If so is he responsible to pay association fees and special assessments for the voted units?

Your answer is complex, and requires precise definitions.

Usually, unbuilt units have no voting rights, because there is no allocated interest in the association's assets for unbuilt units.

If the association president is not the developer, the president has no vested interest in voting for units the president does not own.

If the president is the developer, the developer may be able to exude development or declarant's rights that address unbuilt units.

Your best answer will be available from an association-savvy attorney in your local area. Be prepared to show evidence of the motions being voted upon and who is voting, based on what authority.

Bottom line, it appears to be patently unfair for current owners to be burdened financially for unbuilt units, if no one else is paying the allocated interest share for those units.