I’m currently on a shared hosting plan, I’m thinking of trying a VPS, is their a cost to upgrade? If I change my mind can I switch back to shared? Is there a cost for downgrading if I do?
You can move your domains back and forth from shared to VPS and back. The costs for VPS are higher than shared hosting. Costs are detailed on http://dreamhost.com/hosting/vps/
This article has more details on how to migrate domains to VPS:
To move back to shared hosting, delete the VPS and its content will be migrated to a shared account.
Thanks for the help @smaffulli!!!
One more question… My SQL databases are still hosted on shared servers, if I cancel my shared hosting plan, can I still keep the DBs on their shared servers?
Yes, shared MySQL databases are included in the VPS and you can safely cancel the shared hosting billing once the domains/sites have migrated to VPS.