https://21pbn.com is no doubt a short cut to marketing and results can be achieved at a rapid speed through this service, but people make a lot of mistakes and blunders in setting up such a network. If this thing is done right, it would produce sufficient results but on the other hand, it would create a lot of trouble for you if your website is once delisted. Therefore, you cannot rely on all the SEO service providers in this regard, you would have to discuss with your SEO expert whether he would use any such mechanism to bring your site to the top rank? If yes, then discuss the viability of his plan because it is your website and not his if it is deindexed only you would have to face the consequences. There are some things that can be done in order to avoid deindexing of your website. These are discussed below:
Things to avoid:
Number of posts on a particular website. This is one very crucial point and you should focus on this more than another thing. When people start optimizing their websites for search engines, they start publishing as much content as possible which is not true for a good campaign. You should limit the posts to around less than 10 because more than this would alert google and it might start inspection which would result in unwanted consequences.
Further, hosting through a single service provider is not a desirable thing, you should consider this fact that it would leave a foot print and you would be caught. https://21pbn.comis very good in this regard, they take good care of this fact and does not let your website get deindexed just because of the fact that the whole network was on the same hosting server. These are small points but should be catered in order to save yourself from trouble.