How pay works

Wages are held while you work and paid out together, the way a real paycheck is.

Payday

Wages build up as you work, and are paid every 7 Minecraft days. A Minecraft day is 20 real minutes, so payday comes about every 2 hours 20 minutes of real time, which means an evening's work is paid before you log off.
The server keeps 2.5% of each paycheck as tax, for the Treasury.
One paycheck can pay at most $2,000. Anything earned past that in one cycle is not paid.

Jobs

You can hold 3 jobs at once. If you resign from one, there is a 24 hour wait before you can take another, but only after you have held a full set once. Filling an empty slot is free.
With no job at all, you are paid $250 for every pay cycle you spend online, and /beg gives a little help on a short cooldown.

What does not pay

Pay is for honest work, so a few things are left out on purpose.

Blocks you placed. Breaking a block somebody placed, or placing on a spot that has already paid, pays nothing.
Unripe crops. Farmers are paid for fully grown crops.
Fishing in one spot. You have to move now and then. Stay put and the wage stops until you take a step.
Creative and spectator mode.

Selling to other players

This pays better than the server does, and it is not only for shop owners. Most stores only sell, but a sign shop can also buy:

A blue [Shop] sign sells. Right-click it to buy what is in the chest.
A red [Buying] sign buys. Right-click it with the item in your bag and the shop's owner pays you, from their balance, straight into yours. The items go into their chest.
Nothing is taken on the way, so you get the full price on the sign. If the shop is full or the owner cannot pay right now, it tells you.

Not many players have set up buying signs yet, so if you want to sell something, look for one in /store. Better still, put one up yourself: write [buy] on the first line, how many on the second and the price on the third, with one of the item in the chest, or use /signshop new and pick Buying. People then sell to you at the price you chose, and you get the materials you need without hunting for them.

Selling to the server

The server will buy most things with /sell, but it is a safety net, not a living. Prices are low, they fall as more of an item is sold and recover over time, and there is a daily limit at full price. Other players pay more, so check /store first.