I agree with Christina that looking for ways to gain experience and learn at the same time is a good place to start.
There have been various VA mentoring programs set up over the years, there was/is even a
virtual assistant mentoring program here at VAF, but they eventually stop operating for the same reason - the VAs who are established enough to mentor are busy actually running their own businesses and working with clients.
There are of course VAs who coach and train new VAs, and there are also tons of products and classes out there that are more self-study.
There are also often university professors looking for admin interns or assistants, some high schools give credit in exchange for your service in the offices, etc.
There are many ways for you to start building the experience and the confidence you need to make this happen.
But the thing about being a business owner (virtual assistant or otherwise) is that you can't really 'wing it' - you either have what it takes to start and run a business or you don't. And that's only one piece of the puzzle - you also have to be able to deliver to par with your clients' needs expectations. So in that regard, getting some experience as an in-house admin could be a good way for you to go.
I will say that I don't believe your age precludes you from being a business owner or an entrepreneur - or even a VA for that matter. If you sit down and really think about what you CAN do, maybe you'll come to realize you do have some specialized skills after all and can build a service business around that. Not every VA knows how to use Quickbooks (I don't!

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Wishing you much success!