Possible to join GTA V Heist without high-end apartment and/or less than level 12?

The requirements for playing the heists are plastered all over the internet:

• Need a high-end apartment with a planning board
• Need to be level 12

However, some places says you need to be level 12 to host the heist where as other places says that heists unlock at level 12.

What is correct?

A level 6 (example), can he join a heist, provided that someone else that meets the requirements hosts it? Or does everybody need to be level 12 (or higher) and have a high-end apartment?

Solution 1:

You can join someone else's heist if they invite you, regardless of level or residence.

you only NEED to be level 12 and own an apartment to be the heist LEADER / HOST the heists.

Solution 2:

If you are level 12 and own a high-end apartment you will get a call from Lester. He will tell you that it is now possible to join heists and plan them. I am level 4 now and I was able to join my friends on a heist.