I used to lament, "oh, if only I were SAG, then I'd be auditioning all the time!" Well, let me assure you, since I became eligible six years ago, I still have not found a reason to join yet. My commercial agent says to stay SAG-E so that he can also submit me on non-union commercials, and my theatrical agent says to join when I absolutely have to.
If you are just out of college and have little on your resume, good agents at a good agency will not care. If you're young and can play under 18, they will not expect you to be union at all. When I was chauffeuring my 14 year old friend to all her pilot-series-regular and top-network-guest-star auditions, it didn't matter one lick that she was still non-union. They will Taft Hartley you in a second if they like you.
How did I get eligible? I joined Aftra, booked a co-star role on an Aftra show, and one year later sent in a letter asking to join through their sister-union clause. The very next day, I booked a SAG commercial. Go figure.
But shit, folks, we're in the new decade of the new millennium! Cameras are cheap, your friends are all great actors stuck waiting tables and you write decently. Make your own future. Make a webseries! And Taft-Hartley yourself and all your friends!
How? By reading this.
If you're a smart, creative actor, seriously, go SAG yourself. Be pro-active, and be pro-actor!