Shift Lens disabled (left) and enabled (right) to
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allow capturing the entire building while keeping the camera level, thus creating straight vertical lines
In the case of architectural renders, a three point perspective is not always desired as it makes the building look like it's falling away from the viewer. To create a two point perspective (where the verticals are parallel) you have to keep the camera level to the horizon but this might begin to cut off the top of the building while having too much of the ground in the image. You could move the camera further away from the buidling to capture it all and then crop the image to retain the revelant parts, but this is not always possible as other buildings might get in the way.
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After you have leveled the camera, you should navigate the camera in the viewport only by panning (Alt+MMB) to avoid rotating it up/down and thus creating a three point perspective again. Once you have the view you want, use the Shift Lens parameters to move the frame up/down/left/right.
