1st Video Patched

In my experience in making legit GTA V cash I've always found the best ways are those that don't involve dishing out ammo, as well as having to fight in general.

The least spent is the way to gain the most.
So where does that leave you?
While most missions require you to expel lots of ammo and armor I've found the nightclub and the car running business are the most passive.

The night club passively will generate 10k every 48Mins or 2 in game days.

The car running business can vary, If you however can secure a collection you can make 1Mil in a single sale (with a group of 4)

For the nightclub I recommend using this money to primarily pay your expenses, mainly being staff charges and mechanic.

For the car running when sourcing a car look at the plate number if the plate is like "T0P SP33D" or something in that nature go get the car.
If its a normal plate don't even waste time and resource a car till you get a high end plate.
Buy a cargobob if you don't earn one this is the fastest safest and easiest way to go about the car business.

Just be careful to not ruin the car!

If you need quick money there are some really basic ways to earn some quick cash no this wont earn you a ton but these methods may just help you fund a new business or a glitch!

1.) Robbing stores [1k Per store, 5Mins per store, 6 stores 1/2Hr, 6k 1/2Hr, 12 stores 1Hr, 12k 1Hr]
2.) Selling street cars (Preferably a SUV) [5k Per car, 10Mins per car, 6 cars 1Hr, 30k 1Hr]
3.) Downgrading property
4.) The Red Dead bounty and treasure missions [250k]
5.) Race [ Average 10k per race]
6.) Free mode challenges (Ex: business battles) [12k-25k]
7.) AFK playlists (Look this up as you'll have to create your own) [100k 1 Day]