Your 20s might be just the start of your adult life, but you want that start to be a good one. Some think your 20s are the time to live it up, and you can buckle down and get serious once you're in your 30s. This might be true in some regards, but when it comes to your money, it pays to think seriously about it no matter what age you are.

Below, I outline three financial milestones that everyone should strive to reach by the time they turn 30, if not sooner. There are no hard-and-fast rules that say you need to do these things by 30, but you'll make managing your future finances a lot easier if you do.

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1. Have an emergency fund

An emergency fund is a stockpile of cash (usually three to six months' worth of living expenses) that you keep on hand in case an unexpected expense arises. This is money you use for medical bills, home and auto repairs, or to help cover your basic expenses if you lose your job. 

It's important to have an emergency fund at every age, but it's especially important while you're young. If you don't have one and experience an expensive emergency, you might have to take on credit card debt. That can lead to a costly debt cycle that could take years or even decades to get out of. Meanwhile, you're unable to prepare for future emergencies or save for your long-term goals.

Make a list of all your monthly expenses and then multiply this by three. That's the minimum amount you should have in an emergency fund. If you have a high-deductible health insurance plan, make sure your emergency fund contains at least enough money to cover this, unless you're saving for your deductible in a health savings account (HSA). Check in once per year to see if you need to increase your emergency fund, and always replenish your fund after you use it.

2. Create a plan for debt repayment

Planning how you're going to pay off your debts now can help you get out of debt more quickly so you can put money toward your other financial goals. List all the debts you have, including student loans, credit cards, and installment loans like car loans or a mortgage. Note their balances, minimum payments, and interest rates.

If you're trying to pay as little as you can, you should prioritize the debts with the highest interest rates first. Make the minimum payment on all of your debts to avoid late fees, but then use any extra money you have toward the debt with the highest interest rate first. When that's paid off, move onto the debt with the next-highest interest rate, and so on. 

Try making changes to your budget if you're struggling to make progress with debt repayment. Cut unnecessary expenses and look for ways to lower necessary expenses, like keeping your thermostat a few degrees higher or lower than normal. You might also consider working a little extra here and there to get some more money coming in. 

3. Open a retirement account and start contributing

Retirement might be decades away, but you should start saving for it as soon as possible. The contributions you make in your 20s will have 30 to 40 years to grow before you'll need to draw upon them, so they're a lot more valuable than your later contributions, which won't appreciate in value as much. 

To give you some idea of what I mean, consider $100 invested when you were 25. If it earned a 7% average annual rate of return, it would be worth nearly $1,500 by the time you're 65. If you invested that same amount just 10 years later, it would only be worth $761. Contributing as much as you can as early as you can will actually reduce how much of your own money you need to set aside for retirement because you'll have more investment earnings to help you out. 

Your company may offer a 401(k) or you can open an IRA on your own. You're allowed to contribute up to $19,500 to a 401(k) in 2020 or $6,000 to an IRA. Adults 50 and older may contribute an extra $6,500 to a 401(k) and an extra $1,000 to an IRA. Don't exceed these limits or you'll pay a 6% annual penalty on the excess until you withdraw it.

If you tackle these three things in your 20s, you will make your life a lot easier because you'll be prepared for emergencies and well on your way to achieving some of your long-term financial goals. If you haven't done any of these yet, start working on them today and you'll enter your 30s ready for whatever comes next.