I'm a 45-year-old single parent with 3 kids and $450,000 in savings — can I retire comfortably in 7 years and achieve a passive income of $90,000?

Many costs of early retirement to consider

Before you decide if you can retire early, you need to consider all of the extra costs that are going to come along with leaving work so soon.

First and foremost, you aren't going to qualify for Social Security retirement benefits for at least a decade — and if you want to max out your benefits, you'd have to wait almost two decades until age 70. So, you'll be completely reliant on your investments to support you until that time.

You're also going to have 13 years until you become eligible for Medicare. Since you're a single parent, you can't count on a spouse to provide access to a workplace health plan. You'll need to buy coverage on the individual market, which can be expensive and may not be as comprehensive as you're used to if you've always had a plan at work.

If you have three kids, you may also want to contribute to their college costs in addition to any other type of support. The younger they are, the more dependent on you they may be.

Before you determine if you can generate $90,000 in passive annual income from your savings, it's really important to make sure that you can afford all of these costs on top of your routine spending.

There's also an added obstacle: You typically can't take money out of tax-advantaged retirement plans until you're aged 59.5 without paying a penalty for early withdrawals. If you have a 401(k), the IRS rule of 55 may allow you to begin withdrawals earlier — but still not at age 52.

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Can your savings produce $90,000 in income?

The next thing you'd need to look at is whether your savings can produce the desired $90,000 (or whatever amount you need after a careful look at expenses).

You don't want to take too much money out of your investment accounts too soon or you'll run those accounts dry. One common rule of thumb says you can withdraw 4% in year one, then adjust for inflation. However, this rule is designed to make sure your money lasts for 30 years. If you're retiring at 52, you likely want it to last even longer so you may want to be more conservative.

Still, assuming you follow the 4% rule, a $450,000 nest egg isn't going to cut it. It would initially produce just $18,000 — a far cry from $90,000. Now, you do have seven years left for your money to grow, but you'd need $2.25 million in order for your investments to produce your desired income. With seven years left to invest, you'd need to set aside around $12,000 per month to hit a $2.25 million target on time, assuming an aggressive 10% average annual rate of return.

Ultimately, the reality is that you probably aren't going to be able to retire in seven years and achieve such a high income unless you drastically scale down your expectations of what your life will look like or you can save a fortune over the next few years. Granted, these calculations don't include Social Security income you may get when you're older, but it's still an incredibly steep hill to climb.

The good news is that you are still young and can still achieve a healthy early retirement by a more reasonable age of around age 60. Assuming you were able to maintain a 10% average annual rate of return, you could hit that $2.25 million target if you saved around $970 per month over 15 years. By then, you'd also be closer to Social Security and Medicare eligibility age and be able to access retirement accounts penalty-free. Plus, your children may be out of the house, freeing up more money.