I think it's totally possible to build a $100,000 share portfolio by 30 years old.
It isn't possible for everyone to do. If you're earning minimum wage then most of your money is probably going towards paying for the bills and essentials, which doesn't leave much left for investing. But it's not impossible and you can certainly build something of a portfolio.
For people that have some spending flexibility, it's much easier to build a $100,000 portfolio. But, it won't happen by accident. You have to diligently save and invest month after month, year after year.
Building an impressive portfolio before you turn 30 takes dedication and limiting spending today to benefit tomorrow. But you don't necessarily need to live on rice and baked beans.
Most people don't start earning a decent income until they come out of university. Perhaps that's at 21, 22, 23 or older depending on what you're studying for.
The share market has returned a historical average of 10% per annum over the long-term. There are quite a few diverse exchange-traded funds (ETFs) which may be candidates to deliver that type of return over the long-term including iShares S&P 500 ETF (ASX: IVV), Vanguard Australian Share ETF (ASX: VAS) and Vanguard MSCI Index International Shares ETF (ASX: VGS).
If you can invest $1,000 a month into shares (starting at $0 on day one) and it keeps returning 10% a year it would take under seven years to reach $100,000 according to Moneysmart's compound interest calculator.
Maybe you don't have $1,000 a month to invest. But time can be your friend when it comes to compound interest. The earlier you start investing the better. If you can only invest $750 a month it take just under eight years to reach $100,000.
Maybe your budget only allows for $500 a month. Even then it would take less than 11 years. So if you can just start investing when you're 18 or 19 and invest $500 a month for the entire time you'd still reach the goal. It would definitely be possible to start investing small and ramp up the investing as you get older.
Foolish takeaway
Investing something is better than investing nothing. You just have to start and keep going. There will be times when the market is volatile and things don't look so good, but just stick with it. It will be okay over the long-term as long as you have picked a decent investment at the start.