Your best bet is a wireless router. This connects to your broadband connection, and the wireless network in each PC connects to the router.
That way, you only need to leave the router switched on, and each PC can access the web independently.
The alternative is to leave one PC permanently on, and connected to the web.
If you use ADSL, remember to get an ADSL wireless router (comes with ADSL modem fitted internally).
As for the printer - a few routers come with a printserver built-in - connect the printer to the router, and the printer is always available. Alternatively, you can buy a print-server 'dongle' that connects to the parallel port of your printer, and then by Ethernet cable to your router.
See click here for various wireless options