In GTA Online, Survival Mode is a job type that throws waves of enemies at you, increasing in difficulty as the waves continue.
Personally, Survival Mode is one of my favorite jobs. It’s difficult enough to be a challenge, and playing with some friends makes it even better. You also get some nice RP and money as well if you can manage to survive all or most of the waves.
Survival Mode is unlocked at rank 15, but isn’t immediately available. You should receive a call from Ron some time shortly after you reach rank 15, so make sure you answer the call. If you happen to miss it, he should call back after a while.
After speaking to Ron, you’ll receive a mission marker that takes you to Trevor’s house up in Sandy Shores.
Speaking with Trevor will be about what you would normally expect from him.. strange dribble from a seemingly deranged man. He talks about going out and doing some work for him, or something to that effect.
You’ll end up with a mission marker where you’ll do your first Survival job. Once you either complete the job, or fail, Survival Mode will be unlocked, as well as two other Survival Mode maps: Industrial Plant, and Sandy Survival.
You’ll unlock more maps as you rank up. Railyard Survival is unlocked at rank 20, and Processed is unlocked at rank 25.
Keep in mind that Railyard and Processed are a bit more difficult than the initial maps, but they have the same reward for completion.
*Note – Anyone can play a Survival Mode map at any rank if you’re invited by another player that has it unlocked.