@Sampy93
If you do all the heists in 1st person, then you get a bonus - think it's around $500k.
But the best way to make money 'quickly' is to do all the heists in the same order with the same people. If you do that, then you get $1m for each achievement (All in Order and Loyalty). The one thing is that while you are doing this, you can't do any other heist missions inbetween, or with other people, otherwise it will reset the achievement.
If you manage to do that without anyone losing a life, then you get the Criminal Mastermind challenge, which gives you $10m. Which is nice.
4 of us have done the CM challenge (you only get the reward once), and another 3 have done the All in Order and Loyalty bonus. So I would suggest finding 3 others on here who would be up for doing all the heists for the All in Order and Loyalty cash - am sure this would be the quickest way to get $2m (plus all the cash from the actual heists themselves).
Am sure people on here would also be willing to share tips on what to buy etc when starting out.
My advice would be not to worry about buying all the weapons - you end up finding you use the same few ones (there are countless pistols, for example, yet I usually use the AP Pistol and the others are annoyingly ones you have to scroll through when selecting weapons). For a vehicle, I would suggest buying the Armoured Kuruma if you are going to be doing heists or missions as it has the most protection, and is pretty quick (even if you can't see shite when driving in 1st person!)
It costs $525k, but is well worth it:
For Super Cars, I am loving the Osiris - but it is crazy expensive at $1.95m:
The Zentorno is very close in terms of performance (the two of them are the fastest cars in the game) and costs quite a bit less at $725k:
Probably the best value for money Super is the Turismo at $500k:
With all of these, you will also need to factor in the cash needed to fully mod them - which will be another $200k - $300k. A lot of those mods are unlocked after winning races. Am sure people on here would be up for doing a few quick races to help you unlock them.
I should be online around the same time tonight as the wife is out again - so looking forward to finishing up the heist!