The first thing I would do is consider using a supported OS. Redhat discontinued its "redhat linux" OS line, and is now been replaced with its RedHat Enterprise Linux line. You may either want to consider purchasing that OS or a free clone such as CentOS ( http://www.centos.org
). Second, nobody is going to be able to direct you to a tutorial that will give you all you need to start a hosting business. There are various sources of information that you can help to build your own wealth of knowledge with regard to the topic. There is already plenty of information on these forums, and google.com is always a click away.
Running a hosting service is more than just slopping a server on the internet with a few opensource programs running the show. It takes time, persistance, a good grasp of the technologies used, as just a few examples of whats required.
As for installing DNS apache and sendmail on your server, if you visit redhat I believe they still have the docs available on that line of server OS. That said, those programs should already be installed most likely, if not, then type "man up2date" at the command line for information on how to install these packages.