The important aspect of running a WordPress site is to choose a good hosting provider. When you look into the hosting plans of most of the companies the first limitation will be on the number of sites. Let us take an example of Bluehost shared hosting plans as shown below:
If you have one business and one personal site, you need to at least go for the “Plus” plan since the “Basic” plan restricts the number of websites to one. This will cost you additional $3 per month just to add one more website on the same hosting server

== Looking into More Details ==
Most of the popular shared hosting companies (including Bluehost) use cPanel for hosting. cPanel hosting allows you to add unlimited websites using a feature called addon domain. So even the pricing plan shows only one website is allowed per account, actually you can add many sites using addon domain feature of cPanel hosting without upgrading to high priced plans

== How to Use Add-on Domains? ==
Login to your hosting account if you already have one or continue reading this article to understand the concept. Navigate to cPanel section and look for “Assign Domains” option

Click on the “Assign Domains” button to navigate to the next screen and follow the step by step process to create an add-on domain:
 Step 1 – Enter Domain Name 
Enter your domain name in the text box under “Use a domain that is not already associated with your account.” Once the domain name is entered you will see the validation message in the step 2 for verification

 Step 2 – Verifying Ownership 
You need to change the DNS nameservers to your hosting servers in order to verify the ownership. Open your DNS zone editor in a new window and assign the nameservers details. For Bluehost the nameservers are NS1.BLUEHOST.COM and NS2.BLUEHOST.COM. Once the assignment is saved you may need to wait sometime for the DNS changes to propagate. When the changes are effective you will see the confirmation on “ownership verified” under step 2

 Step 3 – Choose Addon Domain 
The next step is to choose the option as addon domain and the definition of addon domain is very simple:

An Addon Domain is a domain name that points to a different subdirectory on your account. This gives you the ability to make it look like an entirely different website

 Step 4 – Choosing Directory and Subdomain 
The final step is to choose the directory and the subdomain or assigning addon domain on your hosting account. You can choose one of the existing directories or create a new directory by entering the name. click on the “Assign this domain” button to add the domain as a subdomain under your hosting account

== How Addon Domain Works? ==
Assume your primary hosting domain is “site1.com” and you want to add an additional domain named “site2.com”. When you add “site2.com” as an addon domain on your hosting account it will act as a subdomain of “site1.com”. You can access “site2.com” in two ways:
- Open direct URL as “site2.com”
- Open the subdomain URL of site1 as “site2.site1.com”. In this case the subdomain name is selected as “site2” in step 4 as explained above

 What’s the Catch? 
The addon domain acts as a subdomain of the primary site in your hosting account. This essentially means you have the limit for addon domain equals to the limit of allowed subdomains. On Bluehost “Basic” plan you can add up to 25 subdomains

If you don’t want users and search engines to access the subdomain URL like “site2.site1.com” then setup a 301 redirect to permanently point the subdomain to the addon domain. This will ensure even someone try to open the URL “site2.site1.com”, it will redirect to “site2.com”.