The cost really depends on how much work you are willing to put in. If you write all - or at least, most of the articles - by yourself then you will end up saving quite a bit of money.
And I do discuss how to create articles fast. It's really not all that hard. It does require work, though.
If you are willing to do the outreach yourself then you could end up saving there as well. But many bloggers expect to be paid in exchange for guest posts - those costs there really is no way to avoid.
So how much this will cost you depends on how much work you are willing to put in. If you want to outsource all of the work, then this could cost you several $100 or even a few $1000+ depending on how big a site you want to build.
If you are willing to write all of the content yourself, then your only costs will be the domain, hosting and the money you pay to bloggers to post your articles on their sites.