Transitioning duplex to smoke-free units

[Rose Ryan]

I'm under contract to buy a duplex in Minneapolis, both units currently occupied. One unit has a family with smokers, the other family seems to be voluntarily-smoke free. 

The family with smokers is month-to-month currently, and wants to sign a new lease with the new owners. I want to keep them there because their unit looks shabby, and if they move out I will have to put $5-10,000 to get the place in better shape and get market rent. If they stay I can use that cash to buy the other duplexes that this seller wants to offload :)

I want my units to be smoke free. I'm wondering if others have experience in transitioning current, smoking, tenants to follow a smoke-free policy. Did it work out? Or did your tenants move along to a new place that allowed smoking? 

I think this family would probably stay, since they are using Section 8 and it is hard to find Section 8 housing in a good neighborhood like this one. But, it's a risk that they would move on, and I would have to invest in spiffing up this unit sooner than I'd like. 

Thanks, all!