You have probably learned a skill and wondered how to make money from it without taking a huge risk. The safest way is to start small while you still have your job.
Pick one service you can offer with the skill you have, not the one you wish you had. If you know spreadsheets, offer cleanup and dashboards. If you write, offer articles or product descriptions.
Start with one or two clients, even at a low rate, to learn the business side: communicating, delivering, and getting paid. The experience matters more than the money at first.
Raise your rates as your confidence grows, and only scale up when demand is consistent. A side income built slowly is far more durable than one built on a leap. Start tiny, deliver well, grow deliberately.