While Rockstar has managed to remove most of the money glitches on GTA 5's mutliplayer mode, GTA Online, a YouTuber has now confirmed that there is a money glitch that actually works.
Watch the video below for a "Car Duplication Glitch 1.12 Update In GTA 5 Online" by YouTuber iJordan1409.
Players would need the help of a friend for this method. First, the player will have to pick the car that they want to duplicate. After this, he should drive it out of their garage.
At this point, the player's friend arms himself with sticky bombs and waits outside the garage before the car is driven out of the garage door. The friend needs to plant two sticky bombs right on the center of the garage door before it opens up.
Just as the car passes, detonate the sticky bombs and watch as the car blows up.
Now, the second car blows up and the exact same car will be spawn right behind the friend. This can then be placed in the garage.
There a few more insturctions to complete the method from the driver's perspective, have a look at the video for all the details.
The YouTuber goes on to explain that this method cannot be performed with super cars for some reason and is restricted to the more regular cars in GTA 5 and GTA Online.