[DOESN'T WORK ANYMORE] Actually Working Solo Money Glitch

That's probably the worst garage to do the checkpoint trick (due to taking too much time to check if your door will open correctly, but It still works, slowlier). Try finding one where you don't have a pole in the middle of the checkpoint, and with your phone open, walk there and do that. Also, you need a third of the speed you had in that video.

It's a good representation, eventually you get the trick and it just becomes easier each time. Remember that the checkpoint part only has to be done once, unlike the Gerald part, which is how you dupe the car.

First time it despawned before I entered the garage (I looked away, looked back and poof it was gone) and the second time I made sure not to look away while driving the dupe into the garage but when I got out it was gone anyway.

Ok look here my dudes. I can get it to dupe but the original is despawning on me. Done flushed 300k down the toilet. I need a mate to help me tonight. I will pay you 200k just for helping me. I need you to watch the original so it don't despawn on me while I'm going in and out of my garage. Hit me up. Erowidian

I don't think you can pay someone in-game. However, this is a quite cooperative crew and I'm sure you'll find someone who's willing to do this. You might want to consider using slack for things like this, because you'll probably reach more players that are currently online in-game.

I haven't got banned but I'm really calm about it because there are two types of bans.

1) Permanent for having something "extra" in your game files.
The game can scan your game files and if it finds a trainer that shouldn't be there it bans you for like 3000 years or something.

2) Non-permenent for bad behaviour.
That means picking up money bags from cheaters, duplicating cars and all the stuff that doesn't require cheats (extra game files). The first time you get convicted of this results in a 30 day ban. The second time you get a 90 day ban and only if you get yourself caught the third time you get the 3000 years. So just keep going, keep duplicating and in the worst case scenario you'll have to find a different game to play for a month. No big deal.

That's an interesting thought. However, I almost always dupe the Schafter and I use the Murrieta Heights and 331 Supply St. garages and it has never happened before which makes me think it's just random.