I think it still works, as people are still doing it, now with the M4 instead of the Merc, but I can't say personally if it does as I only did it once as the digital version takes a hell of a lot longer to do. Once was enough for me lol.
How to:
1. While on patch 1.01, buy M4(s) Each one will get you 20 million, so 4 M4s will be 80 mil.
Make sure you are not using the car, just be currently driving a different car.
2. a. If using a disk, delete the 1.01 patch in the game data (NOT SAVED DATA)
b. If a digital version, delete the entire game.
3. Disk users just start up the game again but don't download patch 1.01 when it asks you to.
Digital users, download entire game again, again when you start it, don't download patch
1.01.
4. Sell 1 M4, (note the cars name in the garage will not be M4, it'll be just numbers.)
5. Buy what you want till you have no credits or not very much, repeat step 4 and 5 until you
are satisfied, or ran out of money/M4s
6. Quit game.
7. Start the game again, and install the patch 1.01
8. Repeat if you wish.