okay so i am playing the game, its pretty great. im pretty far in the story mode. but my question is, can i do heists and roberies outside of the main missions? if so, how?

also, what are fastest ways to make money outside of main missions?

if anybody has some cool things to do outside of main missions feel free to share as well

thanks!

Stocks are the way to make that fast cash, there is a certain way to do it, its been awhile since I have played. I know thats how I made a extra bit of money. i would just buy stuff that fell alot in value and buy cheap and sell high. I am sure that there is a certain way you could make much more with a guide or some more specific tips, nothing a google search couldnt handle.

Well, didn't played that much GTA V, but here we go:

1) Heists are on main missions/side quests. But you can do it on GTA Online, so that is my recommendation if you just want to go and do a heist/race.

2) Stock market. A lot of history missions will make you do something that will change the stock value of a in-game company. Knowing that, you can play with stocks (you can use it from any computer. Available after the Life Invader mission). This guide is nice too: http://www.ign.com/wikis/gta-5/How_to_Make_Money_in_GTA_5.

3) Do the Trevor side missions, they are great. The ones with Michael and his son are good too. I like going out with Franklin and Chop, only because whe you got in a fight, the dog goes crazy and attacks everyone that attacks you. My last recomendation is to watch TV in game. Every TV passes some crazy and funny cartoons made for the game that satirize other games/persons/politics. Sometimes I stay hours watching them.

how do i do heists that are side missions? do i do the strangers/freaks side missions? or some other way?

ill have to take a look at that stock market lol. 

and yeah i watched a bit of tv, its pretty funny actually XD

I presume you are talking about the singleplayer but i think heists are coming to GTA online soon.

But for singleplayer. Use stocks, especially around the time you do the assassination missions.
I wish there were extra optional heists because they were the best

The more side missions you do, more will appear. Some of them will be heists, assassinations and so on. The stranger missios are cool, I did some with Franklin that you have to tow cars. It's funny because you go with a crazy addicted woman that is ugly as hell but keeps trying to hit Franklin. Poor bastard. GTA Online is the easiest way to choose missions, but I haven't played much of it. Try the Franklin assassination missions too.