I had a few items that were required that I initially was willing to overlook, like missing smoke detectors and simple things like that.

Also, technically they have failed to comply with the lease by smoking on the property.

HML on buy and hold will result in little to no cash flow unless your getting a smoking deal.and at the end of the day you really end up in far worse position since the asset has not really appreciated and you have paid 20% apr for your funds instead of 10% or something like that.Nope HML is not the answer here ...

None of the woodwork was painted, the downstairs unit smelled like someone smoked two packs a day for 50 years in there, and there is a lot of personal property throughout, but it definitely seems like a good deal.  

Anyone have any advice on what to look for or how to vet investors that are blowing smoke?

I had to replace a 2nd floor window that had been there for 100 years... modify all the stairways and deck railings... hard wire smoke detectors and on and on...

Installing smoke detectors that haven't been wired to function is giving a false sense of securing.

The landlord is requiring a 2 year lease, no pets, no smoking.

Smoking inside raises fire risk, obviously.  

If they can bring you a smoking deal even better.