The NAR REPA training is gone now? That's news to me. I suppose that it wasn't getting enough activity anymore to support keeping it. There are other sources out there to get some real estate VA training like Pam Ivey's
REVA Institute.
To be a REVA, you do not necessarily have to be "Certified" if you have the experience in the real estate industry. I didn't when I started, but I had several years of experience under my belt working in the industry.
But if you don't have any real estate industry experience and you do want to break into it, then definitely look into training. In the meantime, don't let that halt your business startup efforts. Start providing just general admin services (or whatever experience you have) to other businesses as well as agents, and you will gain much through experience.