Starting a podcast focused on their academic field of expertise can provide professors with a platform to engage with a broader audience. They can discuss recent research, interview other experts, and delve into educational topics, potentially earning through sponsorship and advertising.

Professors experienced in securing research grants can offer consulting services in grant writing. They can assist other researchers or academic departments in preparing and submitting grant proposals to secure funding for their projects.

Partnering with other universities or educational institutions as a guest lecturer can be a great way for professors to earn extra income. They can share their specialized knowledge and gain exposure to a new group of students and colleagues.

Professors well-versed in academic writing can offer editing services to fellow academics, researchers, and students. They can help refine theses, dissertations, journal articles, and grant applications to ensure clarity, coherence, and quality.

Creating and selling online courses through platforms like Udemy, Coursera, or their own website allows professors to share their knowledge with a global audience. They can design courses in their expertise, offering video lectures, reading materials, and assessments.

Writing and publishing books related to their academic discipline or other areas of interest is a lucrative side hustle. Professors can write textbooks, guidebooks, or even popular science books to reach a wider audience and generate royalties.

As experts in their fields, professors can book speaking engagements at conferences, seminars, and corporate events. They can share insights on their research, offer motivational talks, or conduct workshops in their area of knowledge.

Professors can provide consulting services to businesses, government agencies, or non-profits. They can offer their expertise in areas like organizational behavior, education policies, scientific research, or technical development, depending on their discipline.

Offering online tutoring services in the subjects they specialize in allows professors to help students from around the world. They can use platforms like Tutor.com, Chegg, or even create their own websites to reach potential clients.

Professors can leverage their expertise in their field by writing articles, research papers, or blog posts for educational websites, academic journals, or popular media outlets. This can help them share their knowledge, build their reputation, and earn extra income.