I don't think you'll have any problems finding a server that can do that for you. You may need some additional IPs for the SSL certificates but, that's a perfectly justified reason to get additional IPs. I suggest you look at www.layeredtech.com if you're on a tight budget or you can check out www.gnax.net for some servers on a really nice network. www.defenderhosting.com also gives IPs away for free with proper justification so, you should check them out too.
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It depends on your style of business. If you want the ISP to take care of everything for you such as server management, security audits, monitoring, you may need to look for a managed server package. For your customers to have control, I would recommend CPanel. You may just only need one server for what you have just posted. Here is my opinion on server mgmt levels:
Budget/Unmanaged - For the people who have intermediate-expert level knowledge of servers where they can manage/fix problems on their own.
Managed(usually at a premium) - for people who lack knowledge or do not have the time to spend tackling an issue that may occur.