It was a co-op building in the very very north of Manhattan, area called Inwood. 

Or I could cancel my application for the permit and leave everything as is without enforcement from the town. i.e. keep operating the 4 units but they will not provide a CO which clearly limits the up side down the road when I decide to sell the property.

Unfortunately $100,000 does not buy much in San Diego and I do not have a co-signor. 

The two options i have been given is either A) Have a co-signer.

She couldn’t come up with a single reason why anyone would want a co-op.

Maybe a co-working space?

Through the buildings history there have been previous developers that have partially finished several units, but the building still needs a major renovation to get a CO. 

Aside from that info, maybe it's just a Chicago thing, because around here a co-signer works just fine, as long as that person can meet all of the requirements.

My experience is with college aged young adults and therefore I have ONE responsible party (possibly with a co-signer) on the lease and the others listed as "legally" (per our lease) allowed adult occupants (ALL occupants are listed on the lease and they are just another occupant although we have run credit & background on them).

I've been doing research all day and found that houses that have been built before 1938, are not required to have a CO.