Sunset Coast Mansion by kristg is a GTA V Map Editor scene, published as version 1.1 in April 2016. Its pools, garage and yacht belong to an XML placement workflow. The creator page does not provide a FiveM resource installation.
Original Sunset Coast Mansion release
Load the XML in Story Mode
The creator instructs users to extract sunsetmansion.zip and place sunsetmansion.xml in the GTA V root or scripts/AutoloadMaps. In Map Editor, choose Load Map, select XML and enter sunsetmansion. The location reference is in the archive; the creator specifically says to load the map while at the golf course for the pools to spawn.
Keep a backup before adding an autoload map. If objects do not load correctly, the creator suggests loading a different map and trying again. Check your Map Editor and game-version compatibility rather than interpreting this as a guaranteed fix.
Cars and server deployment need separate checks
The page links the Mercedes-Benz G65, McLaren P1, Lamborghini Aventador and Bugatti Veyron as car mods used by the creator. Those credits are not evidence that four vehicle packages are bundled with the mansion. Obtain any separate vehicle from its own creator source.
For FiveM, first establish a suitable conversion, required props and permission to redistribute any included assets. Test object placement, pool behavior, collision and neighboring maps. Copying this XML into server resources or renaming it does not create a verified server map.