There’s a common misconception that the only way to build a Private Blog Network is to use expired domains. This is a not entirely true. The truth is, a Private Blog Network is simply a collection of blogs that are run centrally for the main purpose of manipulating and directing link juice. If that is the working definition, then there are, of course, many ways to do this besides just expired 
domains.
The main reason why many SEOs equate expired domains with PBNs is because expired domains give you a tremendous head start. They overcome many of the headaches involved with building a PBN organically. Still, you can choose to build an organic PBN using free Web 2.0 accounts.
Why would you want to do this? Well, if you’re going to be using backlink building software, you can save a lot of money by using Web 2.0’s blogs. If these get penalized, you would not be out of thousands of dollars because you’ve spent that much money on your own domains. There’s less risk financially speaking, if you use Web 2.0 accounts. Also, you have a lot more leeway as far as how aggressive you can choose to be when building backlinks. Due to the extra flexibility of Web 2.0, a lot of SEOs use these types of blogging platforms to build their PBNs.
Leveraging Free Blogging Platforms
You have to understand that Web 2.0 blogging platforms create DoFollow links. When you build a blog on those platforms, the links that you use in the posts will be DoFollow. While most of them will have a NoFollow tag on blog comments, the blog post content itself and any link it contains will be DoFollow. After all, these are meant to be legitimate self-publishing platforms. Use this to your advantage by building a lot of these, creating the right context, and then harnessing the collective link juice these websites generate to go to either your target site directly, or through an intermediary layer of other blogs.
PBNs don’t have to use your own domain
When you’re using Web 2.0 accounts, you don’t have to use your target site’s domains. Also, you don’t have to use keywords. In fact, I would argue against using keywords as sub-domains on Web 2.0 accounts. They’re very easy to spot; it’s very easy to see that you only set up those websites so that you can farm link juice by naming your Web 2.0 blogs after your target keywords. Doing this makes it quite easy to see your motivations.
This is especially true if even a very shallow reading of your content leads to the conclusion that the content is absolute garbage. You may have used software to generate the content, but the only reason why the Web 2.0 was put together was to target the keyword that is in the name of that blog. Do you see how this all works out? This is why you should try not to use your target keywords for your Web 2.0 names.
You also don’t have to use your own domain name. You can use the sub-domain given by the free blogging platforms, but you have to make sure that those names look natural. I can’t emphasize this enough.
Focus on building context instead
Now that I’ve gotten you to open your mind regarding the possibility of not using keywords in your sub-domain URL and title for your Web 2.0 blog, I need you to focus on context. The whole point of your PBN is to provide link juice. That much is true. However, to maximize that power and avoid getting penalized, you also have to use your PBNs to create context. This means that your whole PBN must target different sub-areas of discussions regarding the general sub-niche or niche that you are targeting. This way, whatever links you generate through this network would be contextual and its value would be much higher.
Don’t use the same content
A lot of people who use Web 2.0 sites are obviously trying to save money, there’s nothing wrong with that. There’s no shame in that game. The 
challenge is, you have to know which parts of your blogs you can save on and which ones you can’t.
Since you’re already saving money on hosting and domain names, you shouldn’t go all the way and try out to also save on content. If you try to spin content using software, this may lead to almost unreadable content. This is going to put your Web 2.0 sites in danger of being banned or penalized. After all, dead PBN sites don’t produce or pass any link juice. You don’t want that to happen.
I would suggest that you spin your content and have it edited so that the quality is at least passable. Alternatively, if you even have a little bit of money, try cheap original content. You’d be surprised as to how cheap original content written by native English speakers can be. There are lots of underemployed college students out there who would love to write for you. Regardless, you need to stuff each Web 2.0 PBN blog with semi-decent quality content.
Create backlinks to each PBN blog
This is where the secret sauce is. Once you’ve set up your PBN blogs using Web 2.0 platforms, the next step is to create backlinks to this vast network of PBN blogs. There are many automated tools like GSA you could use.
One-tier or multi-tier
The next step is to decide whether you want a multi-tier or one-tier system. A one-tier system involves just one set of PBNs and all of them linked to the target site. A multi-tier system is where you create one level of Web 2.0 sites, which then link to another level of Web 2.0 sites. These sites can then either link to another tier of Web 2.0 sites or to your money site.
The goal here is to create a contextual source of links. As lower tiers get more slower or outer tiers get more links from the internet, they concentrate the potency of that link juice and they pump it to either a higher tier or directly to your target site.
Building a PBN that uses Web 2.0 account is not that hard. However, you need scale, and you also need to be careful with how you interlink your websites.