This home also taught me the great importance of not allowing tenants to smoke in the property.

I would also review with the agent what types of safeguards the companies will expect (Hard wired smoke detectors, Central station alarms, extinguishers, etc.) as some of that will be cheaper to do during your rehab rather than laterIf you lease the commercial space out to certain businesses you may have to comply with additional codes. 

If you smell smoke when you enter and your lease says no smoking on the premises I would go ahead and start the eviction process, a tenant that lets that happen once will let it happen again.

@Richard Lovering you mention smoking in the house, is there a no-smoking clause in the current lease agreement they are under?

Purchase price: $1,900,000 Cash invested: $1,700,000 Put in Smoke Detectors (there were none...seriously), CO detector, cured raw sewage in the basement, etc.

But DOM is a good sign as mentioned. 180 days means not a smoking deal almost 100% of the time.

In the upper unit, the tenant has lived there for a number of years and smokes inside the unit - it's definitely going to need some work to address the cigarette smoke/tar build up. 

we do annual- we check smoke detectors, check under sinks for any leaks- kitchen included. 

And you will get smoked on taxes when you sell.

We had one applicant, but decided not to go with him because he said he couldn't control his son's smoking habits.