How do you get free money?

Sell furniture, send you're Sims to better paid Jobs, wait for the dog to get some money, or just wait for you're daily bonus in the post box - theres no quick cheat sorry

Plant peppers in a garden patch it is free and fast and earns you money. Also, every time the dog finds something praise it or have someone praise or play with it. Then it digs up more money faster.

There is no way to get free money other then collecting it from your dog (or cat), getting your daily reward and growning peppers. One of the best ways to get money though is through the Simeon Sprout and growning beans, pumpkins, onions while you sleep. Grow tomatoes at your own risk as you won't always get money from it. (If it goes wrong and a huge plant comes up, don't worry as it actually won't eat your Sims).

You can go to the garden patch and get all your Sims to plant something expensive and use all of your money that you have. The more expensive the plant is the more cash you get.

This is not free but there is a plant you can grow called the simileon sprout that costs about 200 simeleons but once you grow it you grow it you will get more money than how much it costs. You also get daily money as a gift when your Social button is flashing a present sign.

Sometime I see the boy at the mail box and you can watch advertisements to have money or furniture or decorations,...
Don't skip out until you see the "finish" button or you can't watch advertisements again (about 1 day the boy'll appear again) .