Speak, you give your daughter the best advice. Unfortunately if his promises were not in writing the landlord will not have to deliver. The kids could put their money in an escrow account until the repairs are made. This way he cannot accuse them of not paying the rent. However again if it's not in writing, it doesn't exist.
If they bail out and lose their security deposit it will probably be money well spent for a lesson learned. I would also have them call the city inspector office The description of the outside must violate some ordinances. Mayor Ed had been very aggressive in making these slumlords clean up their act. Good luck.
For the frustrated one, taking before and after pictures is crucial as a landlord. I would definitely keep their security deposit. If they take you to small claims court to recoup it, you will have evidence of how they left the place. There are as many slum renters as there are slum lords in our community. Good luck to you.