Web 2.0 Linkbuilding newbie question!

Hello

I read a lot about linking from web 2.0 sites is an effective way to rank our page.I have 2 newbie questions,please forgive me.

1.
Iam thinking about building 50-100web 2.0 sites manually and link them to my money site.
My question is can i use them again and again for my other sites?
What if i pick 50-60 sites randomly and link them to my money site,after i just close the comments to prevent spamming.
And when i need ,i just open them again. Maybe i would let some spam and other links to look natural.It would be my prive blog network.
Is it working?if not what would be the right way?
2.
If it works,should i link them randomly?
3.When i post articles on my web 2.0 sites should i do onpage seo?
Or the link pointing to my site is enough.

Thanks in advance

1. Not a good idea if you acutally make the web 2.0 site. If your fake web 2.0 site is not indexed at all, it means sqaut and won't have the high page rank that these types of site usually carry.
2. Yes, but it really won't in my opinion
3. If you put a decent article up with good keywords it will help a lot. Keep this in mind if you decide to go this method.