I want to create two networks in our office. We want one secure network to service the office computers and one unsecure network to service the public so that we can provide wifi to our overnight guests. How to we create this network (s) and what equipment will we need to do it? Thanks in advance!

The simple way is to keep them completely apart. Use your normal lan within the office. Connect it to nothing else. Then get junky old computer running linux wifi setup for guests connected to internet. "Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10

You have a couple simple options. They do make SOHO level wireless routers capable of providing a "guest" wireless network that is separate from your main network. This would probably be your best bet. However, if you know your stuff, you could create a wireless network that's separate by creating a separate subnet from your main network and use a router to give them both internet access. Thirdly, you could get a second SOHO router and internet connection.