Network design ideas needed

I visited a client yesterday for the first time. He has a small (3 computers) p to p network. He wanted to share printer so I did but while there I noticed no virus detection, no backup and company files are stored on all three computers. I want to help him secure his network and make it a bit more organized. This is what I want to suggest to him: Get Anti Virus. Install 2nd Hard drive in one machine and use that drive as the central location to store all company files. Make backup of company data to CD-R. I dont think he can afford to pay for much more. Is this a good solution?