We don't recommend sending content as an HTML5 email. Although you could send your investor a zip file via email (preferably as a link from cloud storage instead of an attachment), the best way to send them your content is to upload it and send them the URL.
Here are some materials that Justin has put together to help explain the process of uploading content:
For free hosting, there are some workarounds for hosting via cloud services (many cloud services, such as Dropbox, no longer allow their service to be used to host content). Here's an article I found with more information about the workarounds:
There was also a post on the in5 Answer Exchange in which GitHub was used to host content for free:
If you'd like to limit access to your online content, then you can add a password screen:
You can export your InDesign layout as a web app and enable offline cache for your investor to download and later view while offline. Here's more information about making web apps with in5: