I'll jump back in to try and address some stuff:
I looked at this from the perspective of an investment where the downpayment goes into X (X being an initial investment in whatever) and then looking at what comes back (this has to wait until you sell for obvious reasons). Since the absolute cost per month of the two are quite similar in this particular building, it seemed like a fair (or at least straightforward) comparison between renting and buying. Renting would be zero ROI in this case, whereas the credits/principal/tax rebates/renovation costs/etc affect the ROI on that initial investment of X.
u/Jon Bon - I consider principal paydown as a gain in this situation, as a corresponding rent payment would have never come back to me. Again, this equity is somewhat trapped while you're there, but a sale realizes the gain or loss. I understand this is not how a "real" real estate investor would do their numbers.
u/andysandp - Purchase price was 291K (we borrowed closing costs) and sold for 302K. Appreciation of 11K total, but totally flat considering we did some work. This building has been really flat for prices; it's a high-rise and there are 39 identical copies of this floorplan, so we had excellent comps over time. Maybe I should have asked for more though.
u/chesbert - This is something I was quite concerned about at first; I checked our bylaws REALLY carefully before we did AirBnB and there was nothing that prevented it (that actually surprised me). As you know, Chicago is not super friendly towards AirBnB and the building can vote to eliminate short term rentals at any time. Hasn't happened yet in this building, but it is super common. One unit in our building did get a thousand dollar fine, but they were renting out the whole place, instead of just a bedroom.
u/dandarc - it's tucked in the post somewhere, but our building is about a wash for renting versus buying as far as monthly cost. I ignored the cost of mortgage payments/taxes/insurance in my examination, and solely focused on what financial advantages I reaped or suffered solely as a result of being an owner versus a renter.