THERE ARE DIFFERENT WAYS TO GET INTO SAG-aftra.
According to the SAG-AFTRA constitution, if a talent "(h)as worked, is working or is about to work in a position covered by a SAG-AFTRA (or AFTRA or SAG) collective bargaining agreement” then that person is eligible for membership. Simply, if you book a union gig, you're SAG-AFTRA eligible. You do not have to be a union member to get a union job. This is pursuant to federal law.
Vouchers for Background Work
To gain membership to SAG-AFTRA through background work, a person “must have completed three (3) days of work as a background actor under a SAG-AFTRA (or AFTRA or SAG) collective bargaining agreement." Not all background work is covered. You must get a voucher that signifies that the work is a union background job. Three vouchers are required.
If a person is working on a background job or as an extra in a commercial, there may be the rare chance that the director instructs you to have a line of dialogue. This is an upgrade in pay. Also, it makes you now eligible for membership in SAG-AFTRA.
When a member of Actors' Equity or one of three smaller performers unions (AGMA, AGVA, or GIAA) has been in the Union for one year and has performed as a principal in a production under one of those unions' contracts, then that person may also be eligible to join SAG-AFTRA. This is known as “reciprocity” between the unions.
New Media Production
A method used by savvy multi-talented business-minded people in the entertainment industry is to become a producer, finance a union production, and hire yourself.
National Board Determination
When the SAG-AFTRA National Board determines that you are "engaged in work that advances the (union's) active organizing efforts or general goals," you may be admitted membership. This provision is meant primarily for radio and TV broadcasters. #SAGAFTRA