@Bill S.,
Sorry for the confusion. The type of houses I'm talking about in particular would be a single family home with an ADU. Sometimes these ADUs could be a basement suite with kitchen or an apartment with kitchen built on top of a separate garage. Regardless, these houses are not zoned for duplex and are only zoned for single family. Thanks for helping me sort out the vocabulary. It seems like in this industry one misunderstood definition can derail your entire investment.
Everything you said, Bill, was absolutely correct. Knowing now that it's considered an ADU, I was able to dig up a few things in the most recent version of the Denver zoning code that I found interesting.
Section 11.7.1.2.A.3 Such use shall not include residential occupancy in a detached accessory structure offered for rent or for other commercial gain. Residential occupancy in a detached accessory structure is permitted by members of a household occupying the primary structure, or domestic employees and the immediate families of such employees.
If I'm reading this correctly, in the separate garage apartment scenario, I wouldn't even be able to legally rent out that space to someone other than a family member or employee.
Section 11.8.9.2.A.2 The second kitchen shall be used only by the residents or domestic servants; and
So if you decide to add a kitchen to a basement suite but don't get it legally permitted as an ADU, then you basically can't rent that out to anyone.
Thanks for your help, Bill.