What's the URL/control panel for my resold client to login?

If you are using our new control panel, please go to below link.
http://www.HostBuddy.com/support/KB/a1668/whats-the-urlcontrol-panel-for-my-resold-client-to-login.aspx

Your clients can login to the control panel at http://member.mysitepanel.net

How do I get my own URL?

You can simply setup a CNAME record for member.Yourdomain.com to point to member.mysitepanel.net and you'll be able to use http://member.yourdomain.com
Login to your hosting control panel-->DNS manager to add the CNAME record.