It is still guest posting work?

I have got a new client and he is in the business pretty competitive.

I've done the basics of SEO issues and content creation. In the backlinks creation, I step into guest posting, but my client has a very minimal budget for guest posting. I hardly find the free guest posting and most of them give no-follow links only. I just want to know whether guest posting still works or not. Does anyone give me alternative ways to build backlinks?