Administering a PC in a Vacation Rental Home?

mrn121 asks: "Some relatives of mine are preparing their beach house for rental, and they have asked me to assist in setting up some of the on-site technology. One of my ideas was to add a computer with high-speed internet access to the house, but security issues may be overwhelming. I have administered campus computing labs in the past, so I am familiar with locking systems down, but I am curious about what level of security readers might suggest, and how to go about achieving an appropriate balance between security and usability for such an application. On one hand, I don't want renters to clutter the computer with software and useless bookmarks, but on the other hand, I don't want the system to be utterly useless. One major difference between this computer and a lab computer is that I will not have access to the machine for the entire summer, while the house is being rented."