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

You should get the FAILED TO SAVE box right after unplugging your connection before it disconnects you. Then you know it's working.

I don't get it tho. any idea why? It just kicks me from online mode and it takes sweet time to do it (about minute or so).

"10-20 car slots"

I'm out. I'm happy with my 100 cars, actually I still want more. So, yea.

I'm having a tonne of problems with this glitch. I've done some weird ones before like swinging a fully upgraded Sultan into the garage door with a Cargobob but it still worked all of the time.

could you store it without the other disappearing?

Duplicating worked for me after several tries. I can't bypass the cooldown though, disconnecting the lan doesn't work for me on PS4.

So, here's my log of the process if anyone's interested.

I managed to clear up 10 spaces, and even then I had to sell some cars that I didn't really drive often, but wasn't comfortable selling anyway (Huntley S, the mad drift monster aka Lurcher, my first ever bike or the Schafter I have had so much fun with over the years). They were the parts of my collection I hated to see go, but I figured that with the amount of content R* puts in these days, I'd rather have all the money I need for that than a few old rides in my garages for nostalgia's sake.

Anyways, I got myself a regular Felon. After all the upgrades I applied It solld for 154k and some change.

Once I found a reliable lobby, which took me a considerable amount of time, I had the Felon upgraded and 7,774,481$ in the bank. After I was done with all this, selling the 10 dupes (note that you can't sell the original car, it doesn't have the sale option availible), I was at 8,994,591$ after 56 minutes. So that's a bit over 1,2 million $ in under an hour, but with only 10 garage spaces and not factoring in the time it took to find the lobby. Take that for what you will.

My thanks to adam10603 for providing such a comprehensive tutorial.