Newbie question about domains like blogspot.com

I have some doubts in my link building campaigns, with free sites like blogger or wordpress.
Imagine I have two different site:
webpage1.blogspot.com
otherpage.blogspot.com

Google think that they come from different web pages or they think they come from the same domain.

Services like bloguer.com have more or less relevancy than a new domain you can create it myself?

Ignore.

The main advantage of blogger blogs is they tend to do well in the search engines and it's another source of a do follow backlink to your main money making site.

You should not make free platforms like blogger your main money pages but use them as an adjunct

To seriously make money with affiliate marketing or adsense you need your own blog hosted on your server. I don't think you can get around that if you are trying to build a long term business

I know, I use my own sites to do bussiness, but for SEO purposes and get links I'm trying to use these free services and I wonder if they' re useful

Yes, they are useful if used correctly.

Creating 15 different blogspot sites each with content that contains links back to your target is LESS USEFUL than you creating content on 15 different Web 2.0 sites, each linking to each other and to your target (no more than about 3 total links per page).

There's a concept called a "linkwheel" that is pretty popular that describes this in more detail. Do a search on this.

My advice is to take it one step further and NOT create actual wheels, but build "feeder" sites that interlink to each other (and you) in a more random way. This has been working very well for me.