Hi BrokenFaith,
Having taken your advice on searching hotscripts.com, I found an excellent script there that does everything I needed and more. It's called Login-Redirect v1.31 and cam be found here
http://www.mpdolan.com/login_redirect.htm
Once installed, I simply login as admin and create whatever user (client) I need to, assign a username and password, tell the script where to redirect them at login (
http://mywebsite.com/clientswebsite), and it send the user (client) an email complete with a link for them to sign in. All that's left now is to tweak these pages to match my design...
Wow! I would highly recommend making a donation to this guy on his site, a great and useful script! I will be donating soon!