Hi Chris,
Sorry you haven't received any replies to your questions yet. I've been away for a few weeks and completely out of the internet loop. Weird but refreshing.

Anyway, you've got the right idea about building a site that has potential for growth, but I want to throw a little bit of cold water on you if you don't mind.
I would not recommend to anyone getting started that they choose the theme of affiliate marketing as their first niche topic. The problem is that the field is very saturated and it will take you a good long while to break into it in the vast majority of cases.
Instead, consider choosing a subject that is less competitive and something that you already know a good deal about or would really enjoy learning about.
If you have a hobby or special interest, that may be a good place to start. Maybe you know a lot about a subject or field of work from your offline experiences/job. If it is something you enjoy you are much more likely to do well and stick with it until your site gets the rankings and traffic that will cause you to start generating income and get into profit.
Quite often, the 'nichier' the subject the less the competition and the faster you will reach the top in your field.
Hope this helps a little in pointing you in the right direction. Let me know if I can help further.
Blessings,
Angie