Well you could try to do odd jobs for people, but typically from what I see not many people have that many jobs around to honestly make a living off of it, and the jobs that people do give have very little money-reward involved. So it's not that great of a thing.

I'm assuming by "selling" you're meaning selling to the global shop or from a chest shop? If not then you could try selling to a chest shop instead. I believe numerous towns will have chest shops for farming and such, where you could sell to the shop and get a bit more money there than if you had sold to the general shop. I have such a thing at my town farms and in my own shop, and I believe Castaway and Oakvale have this kind of thing as well.

The other thing to try with this kind of selling is to check the chest shops in the spawn market and find some that buy items off you that you normally obtain through your Minecrafting time, and then you could sell to those shops when they have space to sell to it.