Each character has their own individual safehouse. Every safehouse gives the player the opportunity to save the game by sleeping on the bed, heal with a First Aid Kit, change their clothing at a wardrobe, store vehicles in a garage, and watch the in-game television. The player is also able to use drugs (Jimmy's bong in Michael's House, Franklin's bong at the Whispymound Drive property and Trevor's solvent gas in his trailer) and/or drink alcohol as well. Weapons cannot be equipped inside and the beds cannot be used to save by other characters. For example, Franklin cannot save the game in Michael's House, and so on.
Despite a gameplay video showing the ability to search for a safehouse and purchase or go and check it out, this isn't available in the game. The website for searching safehouses claims it is under maintenance, and can only be used in Grand Theft Auto Online.
3671 Whispymound Drive and the Vanilla Unicorn are the only safehouses where every protagonist can enter.
Trevor's Trailer is the only safehouse that can be used by two different protagonists.
Trevor is the only protagonist who owns two safehouses simultaneously if you only include the ones obtained via story mode.
The Clinton Residence becomes unavailable after Hotel Assassination, including the garage. If there was a vehicle inside, it will remain locked inside for the rest of the game and the player won't be able to retrieve it anymore. It's recommended to clear the garage before this mission and move the desired vehicle to the Grove Street Garage or use it as the getaway vehicle and then store it at the new Vinewood Hills safehouse.