Laser toner refills can be expensive. Over the life of the printer, expect to spend many times more on laser toner refill than you paid for the printer itself.
Laser printers have two chief replaceable components: laser toner cartridges and drums. The laser toner is basically the ink for the paper. The drum is the cylindrical metal roller that applies the ink to the paper. Sometimes printers are designed for cartridges and drums to be separately replaceable; other printers are designed for cartridge-and-drum units bought as one. While the laser toner will last only a few thousand pages in most home printers, drums will last tens of thousands of pages. If you have to replace the drum every time you replace the cartridge, your printing costs will increase significantly. Therefore, if you dont yet have a printer, get one with separate slots for a laser toner cartridge and drum.
If your laser toner ever gets low, a warning light will appear on the front panel of your printer. When this happens, dont replace the cartridge just yet. You can put off spending the necessary money by removing the cartridge, shaking it gently back and forth a few times to re-spread the toner, and replacing the cartridge. The warning light might still stay on, but the cartridge will have been manually renewed for a few dozen (or few hundred, in some cases) more pages worth of printing.
The other way you can save on toner is to use the draft function on your computer and printer settings. This will produce printouts that are suitable for your reading, but not suitable for sending out to other people.