Can someone give me some opinions real quick on this model? I am trying to sell it online and it has a good amount of views, but no sales

I put it up for $45, what do you guys think it should be?

Just some random examples I've seen linked in ads here on gamedev.net

http://www.3dmodels-textures.com/models/scifi_low_poly_map.html

http://3drt.com/store/environments/megacity-construction-kit.html

Compared to those your model isn't very competitive at any price. Usually such a large static model isn't useful at all unless it has a full interior that is made in a way that a game can easily be implemented where you can run through the building with stairs etc, or as a prop in a city, in which case you need like 10 different buildings (preferably with variations) that can be placed in the game.

It does have a full interior. I just didn't show it in the previews above because I was trying to make this post short.

It isn't very detailed or realistic. It's missing roof eave structures altogether, questionable concrete-brick wall structure (did you use reference?), simplistic entrance area and blank interiors. With no HVAC / electrics equipment, no door or window frames, undetailed door leaves without hardware such as handles, IMO the model can't be really viewed as close as you have depicted. But the wireframe model doesn't actually look that bad which makes me think much could be improved with texturing job. The concrete texture has strong horizontal lines making it look weird and repetitive and the model has shared UV-texture space meaning same pixel corresponds to more than 1 location on the final model which is often frowned upon.

If you want to make money by modeling buildings you should probably use a lot of reference images or be an actual architect to achieve good and realistic quality.

Anyway you should build large set with many different types of buildings, nobody buys their buildings one by one as the result would be very mismatched. Some people might want to have 1 building their level but that would require more detailed interiors and exteriors wouldn't matter in that case. As a design task those are 2 opposite directions to take any building model so it's important to know which one you are making and trying to sell.

That being said the building model as it currently is should probably be free. But hey, it's good practice even though your first sale might still take some more models and time. :)

I'm going to be honest, the geometry looks easy to create, the texture maps looks a little repetitive. If you created the texture maps, then it depends on the quality (and resolution) of the maps, perhaps they should be in a separate pack.

I think you are on the right track with regards to building creation, as there is a full interior, that's a plus worth mentioning.

For the exterior (façade especially) I think you have a good rough model that needs some more detail before it is worth the $45, perhaps improvements to the windows and doors, some drain pipes, perhaps a fire escape, perhaps a route up to the roof. In particular the doorway and stairs at the front look too simple. The colour scheme could be reviewed too, I think the grey at the edges and separating the floors looks too similar in colour to the walls. Also perhaps there could be some air vents and plumbing pipes.