This question is not asked, or answered enough these days.
If you're old enough to ask this question, my question in response would be 'Why haven't you started yet?' Warren Buffett didn't wait until he was a certain age before he started to invest, and he turned out to be the greatest accumulator of wealth in history.
If you have the desire to invest, then learn what you need to learn - which is more of everything, I guarantee it - and then do it.
I wish that I had learned what I know now in my teens, or even earlier.
The drive to begin investing is a powerful one, and doesn't need to be backed by a large amount of capital.
This makes it ideal for young investors to get started, make decisions, make some mistakes, have successes and begin the learning process.
After all most people learn best by doing, not by reading - so the sooner you get out and do it, the better off you'll be in the long run.
Investing is a wonderful hobby, skill, profession, interest, passion and desire - maybe one of these, maybe all of them.
I envy a young person beginning their investment journey - for they have so much ahead of them, and not just the added bonus of additional accumulated wealth, but also the experiences they have in front of them.
I maintain that there is no ideal age to begin investing, the journey must begin at some stage, and there is no holding off just because you may thing you are too old, or too young, to get started.
Do your homework, learn all you can about your chosen investment vehicles, and specialize in one or more branch of investment.
If your interest is in real estate, consider doing extra courses, go to property functions and speak to as many people in the business as you can.
Learn all you can about property law, conveyancing, title, contracts, marketing, taxation, building and zoning regulations - anything you possibly can.
The more you learn the better off you'll be and the more successful you will be, no matter what you age is when you start investing.