The first thing you would need is fast internet connection like a T1, T3, OC3 etc. Next you will need a good server, not just a scrap PC. Once your website or sites grow large enough it will take the machine down. The third thing you will need is a power backup source. What happens if the power goes out in your area? The webservers should still be running and your clients will get angry if they are not. This is one of the largest expenses but if this doesn't matter skip it. The last thing you need to consider is backup. You can purchase 200+ GB webhost packages now for $6. I recommend getting one of those and creating a daily/weekly/monthly backup storing all of your data on that remote host.