Ready for another career? How to go back to school and save money.

A bad day at work can make anyone dream about switching jobs. But if those scattered thoughts form into a plan to change careers, you might need to dust off your book bag and head back to school.

Hitting the books in your 30s, 40s or 50s requires money at an age when retirement savings and mortgage payments may be top of mind. You can get financial aid as an adult learner, but to keep your spending in check, you’ll have to think strategically.

Make sure your investment is worth it

Before you jump back into caffeine-fueled study sessions, research salary and employment trends in your chosen field — especially if you want to make more money. That’s a realistic goal: Half of adults surveyed who successfully changed careers after age 45 said their income increased, according to a 2015 American Institute for Economic Research report.

The Bureau of Labor Statistics’ Occupational Outlook Handbook can help you find in-demand occupations and their average earnings. Physical therapist assistants, for instance, need an associate’s degree, and demand for them is projected to grow 41% by 2024. The median pay in 2015 was $55,170.

Once you’ve settled on an occupation, consider getting your credentials through a part-time program at a community college or state university.

“If the program you’re in makes it impossible to keep your current job full time, ask if you can work for them part time or on a consulting basis so that you can keep bringing in some cash while going to school,” says Kathryn Hauer, a certified financial planner at Wilson David Investment Advisors in Aiken, South Carolina.

Take advantage of tuition reimbursement and other free money

You’d be especially smart to stay at your current job if your company provides tuition reimbursement, which you can use to pay yourself back for educational expenses. Up to $5,250 in these benefits can be tax-free each year, according to the IRS — as long as it’s put toward tuition, books and supplies.

The Society for Human Resource Management’s 2015 Employee Benefits report found that 56% of the employers surveyed helped workers pay for undergraduate studies and 52% helped them pay for graduate studies. The average maximum benefit was $4,591.

If your company offers tuition reimbursement, ask your human resources representative if the program has any requirements. For example, you may have to stay at the company for a certain amount of time after you graduate.

And be sure to look for private or school-sponsored scholarships for career changers that cover some or all of your school expenses upfront. Education tax breaks, such as the American Opportunity and Lifetime Learning Tax Credits, can also give you some relief at tax time.

Fill out the FAFSA

Submit a Free Application for Federal Student Aid, known as the FAFSA, every year you study so you don’t miss out on federal, state, or school funding. Your eligibility depends on your income and whether and you’re considered independent — not on your field of study or whether you’re a returning student.

“In a lot of ways I would really treat this very similar to someone who is going to college for the first time,” says Brett Tushingham, a certified financial planner and managing member at Tushingham Wealth Strategies in Wilmington, North Carolina.

The FAFSA determines your expected family contribution, or how much you can afford to pay out of pocket for education. If there’s a difference between that amount and your school’s cost, you might be eligible for need-based aid, such as Pell Grants or subsidized student loans.

As an adult student, it’s crucial to keep your student loan borrowing in check. Take on federal student loans, as opposed to private loans, to receive lower interest rates and access to federal student loan forgiveness programs. It’s also wise to choose a school that pledges to meet a high percentage of students’ financial need.

“To think you can’t get any financial aid or help just because you’re 40 years old is incorrect,” Hauer says. “There’s money for people of every age who want to go to college.”

Brianna McGurran is a staff writer at NerdWallet. Email: bmcgurran@nerdwallet.com. Twitter: @briannamcscribe.

 This article first appeared at NerdWallet.