the entry was filled with steel wool by the exterminator, and I caulked all the cracks and put on the fireplace in the summer time to try to smoke them dead.

This is especially true if there is mold caused by a leak upstairs or a unit on the other side of the wall.The close proximity of neighbors - When neighbors cause problems, your tenants will complain about noise, cigarette smoke seeping through their unit, etc.

If they choose to rent a room these will include:No drugs, alcohol, smoking, pets, or guests allowed. 

A three man crew will get in each others' way and undoubtedly one will spend 90% of his time standing around outside on his phone smoking a cigarette.

Separate your emotions from business decisions and you will see through the smoke.

Those that make up reasons why they can't show this and that tend to hide behind smoke and mirrors.Investing in real estate is a relationship business more than anything.

Some towns just have a basic list of requirements (smoke detector, CO detector, etc).

Can anyone who has dealt with smoke odor before review the process I'm planning on using to get rid of it?

Holy smokes @Dan DiFilippo (cool last name, btw), what a post! 

If it's a C property, you'll have a heck of a time finding tenants that don't smoke, and have a credit score of 550+.