How can I use different domains on a WP multisite install?

I want to offer my clients WordPress websites, but want to use WP multisite. I've read multiple articles on using a plugin, not using a plugin, etc.

My clients own their own domain names and want me to host/manage their sites. So I'll be using my main website as the install abc.com.

When you visit one of their sites like client1.com or client2.com, I don't want the domain name to be a subsite.client1.abc.com. I need them to stay on client1.com or client2.com.

I did find a lot of tutorials, but most are with a plugin and some are reporting buggy behavior.  What I've done so far is setup the multisite on my main domain. I've added an external domain(I own it) and pointed that DNS to my server.

I've never done a WP multisite install before so this is my first attempt. I need to know the following:
 - Do I need to install WP into a folder/directory for each hosted domain?
 - Once DNS is pointed to my server, how does client1.com know what to show?
 - I host on Godaddy so should I setup each client as a subdomain?
 - For each sites content, is that managed by each sites individual dashboard?

Any and all help is appreciated.