Half-duplex rehab (cosmetic issue)?

[Vonetta Booker]

I have my eye on a 1/2 duplex for a rehab--however (as is often the case), the exterior looks like crap.  Since the other half has a different owner, I'm wondering if it can work to simply add new siding and landscaping to the whole structure as part of the rehab budget--and offer to take care of the entire cost? I figure it would be a win-win, as the other owner gets his/her property value bumped up for free, while I'm also still improving the value of the rehab. 

Has anyone ever done a 1/2 duplex rehab w/ this option? If you have rehabbed 1/2 duplexes before, how have you handled the common cosmetic issue of mismatched-looking sides?