Grand Theft Auto III – The Definitive Edition

By far the best way to earn a lot of money early in the game is to do the taxi fares.
Every 5 succesful fares you will get a bonus which will increase the higher your streak is.
I managed to get 88 fares in a row collecting way over 500.000 $ during it.
After that I jumped in an ambulance, did the paramedic minigames, adding an additional 150.000 - 180.000 $.
Right after completing the paramedic stuff, I stole me a police car, did 25 levels of vigilante, earning about 150.000 $.
The rest of the money came while doing the firefighter missions, where you will also cash in big.

Of course you will get money for completing missions and collecting packages. But that's peanuts compared to how fast money will come the way I did it.

Any additional tips are welcome, so drop them below!

You can get this achievement at the beginning of the game after "Luigi's Girls". What I did was the Firefighting Side Mission consecutively not ending it, cause the more fires you put out increases with $250 each time so I got the achievement at 78 fires which was around $700,000 in total which took like 50 minutes. It could take you a lil longer considering I already had around $300,000 from doing the 100 Taxi Fares and failing the Ambulance Side Mission multiple times lol. It probably isn't necessary to go for it this achievement at the beginning of the game considering you can possibly get it later in the game from missions and stuff but it all comes down to what you prefer.