1. There is no real profit to make doing it on your own. Your best bet is to contract a third party such as everyone.net. It can't be profitable.
2. If you want to create email aliases, you can use a free DNS service such as mydomain.com, and use the email forwarding feature.
It's not a profitable business hosting email. Unless you have something else to offer.
Not to mention the spam problems can create bandwidth, server load, and even legal issues.