So my wife and I are looking to purchase a triplex. When we went to view the property, one of the units has a strong marijuana smoke smell. This has us worried about the cost of cleaning this smell up. It is likely has baked into the walls and HVAC ducts. We are wondering how much will it cost to fix this? will we need to scrub the walls and replace the HVAC ducts which sounds expensive? I am sure someone on here has dealt with this issue before. 

The property is currently all rented out and we are certain that the current tenants in that unit are smoking weed. The current property owner's property management company seems to be ignoring this issue. If we do move forward with this,  i am planning to either increase rent on this unit to help offset cost of cleaning up the weed smoke damage when their current contract expires in October. Or i can just not renew their lease and get them out of the unit by October. How do you approach this kind of issue? i am worry about dealing with existing tenants that will give me a hard time while i honor their current contract. 

Is this a red flag to pass on this deal? So it is three units of 2b/1b. Each unit is around 1200sqft. Built in 1980's. The seller is asking 334k. It seems like a decent deal for 110k per unit. There's room to increase value. Good location as there are new developments near by.

The property is currently net zero cashflow but has potential to increase cash flow up to $500 a month after some cosmetic updating. My plan is force appreciate each unit as the current tenants leave one unit at a time and slowly increase rent. 

I would appreciate any pieces of wisdom!