Enclosed is a tutorial guide on how to utilize this glitch for your own nefarious means!
1. Use your phone and call Gerald for a job
2. Have your friend bring down a high-level car. I used Benefactor Swartzer Sports.
3. Accept the job from Gerald with both of you sitting in the car.
4. Play the job alone. Do not invite anyone!
5. Instead of doing the job, place the car in your garage. Once that's done, kill yourself and go to free mode.
6. Take the car to San Andreas Customs and sell it. The second after you sell it, click on start at the same time.
7. Go to swap character.
8. You will now have the car and 100k in your garage.
9. Rinse and repeat.
If you're interested in checking out some of my playthroughs of GTA, check out TheNerdGenious on YouTube.