The Bigger Picture
This isn't really a guide, more of a warning, a few pointers to think about and do your own research on. Far be it for me to say how you should organise your online activities and real estate - I'm far from perfect and I've no idea what you're doing. But I do have a few ideas about what I'd do differently if I was starting over.
Market YOU first
If you haven't already, get a domain name for your name and start a blog on it now. If you're just starting out then you're going to feel like you don't have anything to share with the world and who will care about you. But then later when you do want people to know about you is a bit late to start your blog. For credibility and SEO reasons you want a well established blog with lots of post history and it's hard (not impossible) to do that retrospectively.
Think of this as your control centre, the site that will tie everything you do online together. That way you'll be building a natural structure to your sites and blogs. And in the event that you do become successful and have multiple sites you can just send them to you.com
Planning & Organisation
It's obviously best if you can plan out your strategy first and this very much depends on what kind of thing you're going to do. For example, if you're going to do affiliate marketing and build mini-sites, are you going to have a domain name for each one or organise them under a single domain. What website hosting are you going to use? Are you going to have all websites on a single host or spread them over multiple hosts? These kind of questions can have a big impact on SEO - this article is not going to advise what's best, just to make you aware of the issue.
Are you going to be marketing everything you do under your own name? Under a company? What are your email address(es) going to be? What blogs are you going to have? How are you going to inter-link everything you do? What autoresponders are you going to have? What's your sales funnel? What are you going to do for back-end sales? Do you want a PO Box? (your address must appear in your autoresponder messages).
Having a diagram that you maintain with your thoughts in advance or your business as you go along is invaluable and think from the point of view of a visitor - they go here, they receive this email, that sends them here where they get xyz. This is all vague, it's hard to be specific at this point but hopefully in the future I will link to some more specific resources and examples or case studies for this topic.