Are you a web designer and have a number of websites that you have created for your clients?
The easiest and most effective way of managing multiple websites is to host them in one place.
I would advise that you sign up with a web hosting company if you are unable to host the websites on your own. This requires infrastructure like servers and substantial bandwidth. It is also time consuming maintaining this infrastructure like making updates, providing data and power backup. Ensure that you research the web host before signing up. Inquire about the reliability,
customer support among other factors. Choose a web host that allows you host multiple domains and sub-domains with unlimited web space and gives you good bandwidth. Better still you could sign up for a reseller account that allows you easily manage multiple websites. There are web hosts that allow you setup a reseller account and create and manage multiple domains or websites. You create control panels for these accounts where the user can manage their domain or website with very little help from you. The control panel allows them change passwords, create email accounts, etc.
Some web hosts even offer reseller accounts that have a billing manager to manage payments. You can even acquire extra domains at discounted prices. The reseller accounts also have Private Name Servers that you could use to customize your reseller account.
There are web hosting companies that give you dedicated IP addresses from say 1 – 16. Take note of extra features that may be given like free domain name registration.