Yes and Yes.
Dreamhost don't support Wildcard SSL Certificates (which is what you need to have a single cert handle multiple subdomains).
Wilcard certs are somewhere on the other side of "cheap" and require that you run a gamut of bureaucratic red tape for the most part. This aforementioned red tape may, or may not, compromise of sending in dental x-rays no less than 12 months old, blood types of all relatives up to and including 4th cousins twice removed and, if you happen to live in the USofA, a visit from some moonlighting TSA guys for a thorough 'How's Yer Mother?'.
Unique IPs are ~ $3/month, DH SSL cert ~ $15/year.