The blueprint that came with the special edition had "safehouse" triangles placed all over the map. I assume these will be for GTA: Online. I visited each location and snapped an image of the safehouses, apartments and garages. Some may be wrong, I can't be 100% sure, the blueprint map wasn't very precise. These are safehouses that are in the city, I'll add the blaine country area ones (16 or so) at one point.
Imgur Album: http://imgur.com/a/WoXrk
Disappointingly, there is no houses available for purchase online. This means no luxury homes in the Vinewood hills for us.... really hope Rockstar make them available. Anyway, hope you all enjoy!