Yeah, for enterprise you aren't going to roll it out yourself. They'd use a partner company to help you set it up and configure it for their needs to ensure that it can continue to scale and provide monitoring solutions. It's too much for one person to do that.
Where are you hosting it? Onsite? Megacorporation's clod solution? Your cable line? What's your data recovery plan? 200+ users can generate a lot of data. What's the security plan? You do know how to harden every aspect of each subsystem, right? What's the monitoring plan? Not just "is it down" but way more granular for each subsystem. How many tech and phone support people will be on call to help?
You could probably roll it out in a way that would work, but at that scale you should really be using a pro. Especially for a "friend". Don't want a tech problem to kill that friendship.