Download and install the Single Player Garage Mod by mlgthatsme
Make sure you installed ScriptHookV and ScriptHookVDotNet
Move the Folder 'SinglePlayerGarage' into your "Grand Theft Auto Vscripts" directory.
You can delete individual Garages by deleting their respective folder at "Grand Theft Auto VscriptsSinglePlayerGarage".
Try deleting some garages if your game does not load properly after installing this pack