Fishing for food and profit is like an entire industry. It can be financially beneficial, but you need to efficiently catch fish that are big enough to be worth the time and effort.
The rod and tackle are the expensive parts, and cleaning and cooking are nothing compared to the time and effort spent catching the fish. Depending on the fish, you can gut/scale/filet the fish in under 5 minutes. A hot pan or grill plus half a lemon, maybe garlic and/or herbs, and that's going to taste good with practically any fish you can catch.
On the other hand, you could spend hours fishing and catch nothing. You could catch a fish, but it is outside of the size requirements to keep it. You could catch something too small to bother cooking. You could have the fish take your bait and then slip the hook, or break your line. If those events leave you financially in peril, or without food for the day, then your time is probably better spent looking for a job that pays money, rather than fishing.
There's a reason most commercial fishing is done with nets, or why fish are farmed rather than wild caught. Rod fishing can be effective, but it's not a guarantee.