Resources pay for as long as you stand at them. Animals pay once, then you wait. The two do different jobs: one is your steady income, the other is extra income you pick up as you move around.
Four Animals, Four Wait Times
Cow 60 credits / 90 seconds. Sheep 90 credits / 150 seconds. Chicken 35 credits / 55 seconds. Rabbit 30 credits / 80 seconds. All of them are collected with E; coming back before the time is up does nothing. Later islands have animals of their own.
Farming Is Extra Income
An animal pays once, then makes you wait for minutes; a tree pays for as long as you stand at it. Don't make the farm your main income; think of it as an extra you stop by on your way past.
Milk, Wool, Eggs
Animals leave produce along with credits. Milk and eggs go to the kitchen, wool goes to the loom. You can sell the leftovers at the Port. If you hit animals they fight back; they drop meat and hide.
Fish: The Only Variable Income
A tree always pays 8 credits per hit. Fish don't: with a basic rod you average ~101 credits per cast, but a Moonfish pays 500 in one go, and the rarest, the Driftwhale, brings 1,100. A fish pays its credits right away and also drops into your bag: cook it in the kitchen or sell it at the Port. A better rod brings rare fish more often.
Keep the animal timings in mind and plan your route around them: collect on your way out of base and stop by again on the way back. Fill the time in between with trees and rocks and you stack both incomes on top of each other.