If you are with one of the large HMOs in California, or perhaps with the VA, they may have a tendency to throw an advanced metastatic prostate cancer patient into one large pool and pour in some sequential "standard of care", and see what works, and what doesn't work, without regard to individual germline or tumor/mets genetics. (Cost/benefits considerations might be at play behind the scenes, too.)
Being advanced metastatic myself, in 2016 I was referred by UCSF for family germline testing at their BRCA clinic at 1600 Divisadero Street, H Building, 4th Floor, San Francisco, CA 94115. (415) 353-9797
I did some family history documentation ahead of time, followed by a saliva sample that was sent to Ambry Genetics in Southern California. The particular test I had was the "CancerNext" test, which tested more genes than a similar "ProstateNext" that Ambry Genetics does. In my case, there were looking to rule out if I may have inherited any BRCA-type or other mutations that might be actionable, beyond the usual standard of care for castrate resistant metastatic prostate cancer. (example: BRCA - LYNPARZA™ (olaparib))
Just last week, another man in a support group I attend was offered a different genetic test, involving a blood draw, after a failed attempt to obtain a sufficient bone biopsy sample of a "met" from his pelvis. It was the Guardant360 test, testing for many of the same mutated genes, but via a method that finds them in the form of circulating cell-free DNA (cfDNA). Google "Guardant360 how it works".
As for insurance and affordability issues, if one cannot get them covered by an HMO or insurance, the costs are not astronomical, and something might be worked-out with the companies for $ assistance.
For men who may be asking such questions either right after initial biopsy or surgery with pathology tissue available, there are other genetic tests that may be used to help assess the cancer, and the likelihood of aggressiveness or recurrence. The OncotypeDX GPS and Prolaris assays are discussed here in a blurb from UCSF./urology.ucsf.edu/prostate-cancer-gene-expression-testing-at-ucsf