I want to build websites for others. I want to map multiple domain names into the same DreamHost hosting diskspace. Is that what a subdomain is for? Each of these websites are going to be very small, so I want to conserve disk space and hosting fees. Is this possible?
You’re fine. You get unlimited disk space, so there’s no problem there. This is all included in your hosting plan, so there are no additional fees.
I build and host sites for others, so I create a new FTP user for each domain I create. This way I can hand it off to others for administration.
Just be aware that you are ultimately responsible for what goes on in these websites, so just keep it sane and legal.
Dreamhost offers unlimited domains and sub-domains.