Basically: either you or the seller will be obtaining a CO from a municipality prior to closing, and, if a CO is granted, that's good evidence that there are no open permits, violations, whatever else from the city regarding that house.

And be careful with HOA's - I can tell you some interesting stories about a Co-op rental in Florida.  

I will allow a co-signer to average up the score (in my area it's necessary as I have a lot of low or no credit renters - usually students) but her cosigner has apparently gotten cold feet. 

My question comes from a co-worker and I thought that you all may be the best place to find answers or direction. 

You should try to get the duplex in your name right off the bat, using your dad as a co-signer.

Is there a co-tenant anchor clause agreement where the other tenants can walk from their agreement if the anchor leaves??

In Baltimore I was able to get a a CO (here we call it Use and Occupancy U&O) With a quick inspection and several minor repairs.

Whether I'm required to do it or not, each floor has a fire extinguisher, every bedroom has a smoke alarm, every hallway outside a bedroom has a CO alarm.  

I've heard both recommendations that you should not have your spouse on title and others say that both can be on title as long as they're not a co-borrower. 

If they would be acceptable with a co-signer or a guarantor, then the co-signer or guarantor should put up that move in money before the move in.