Each website should be hosted in different account so that proper resources can be allocated to the website. But there are certain websites that are for informational purpose and do not expect much traffic. One cannot afford to waste useful resources on such websites; at the same time, the existence of such a website matters. A solution to this situation is given by addon domains.
Addon domains allow you to host multiple websites in a single account. All the resources of a single account are shared between your main website and your websites with addon domain. Check if the addon domains available in your plan are sufficient for your purpose.