You would need to keep your main computer turned on.
I have found LogMeIn the easiest way to remotely log into the office computers. Search through the forum for a lot of information about it as well as other options, but...
There are free and paid versions. The paid version includes the ability to print and transfer files. Free version is more than adequate for basic remote access.
You download the program from the site and create a login with the website. To access log into the website and click on your computer.
I actually have all of my computers connected to logmein since I am also the IT person and I can remotely monitor and repair issues.
