Building an AK will cost you more than if you buy one already put together. Putting together an AK isn't like putting together an AR. You will need a machine shop/gunsmith, as well as someone to refinish the rifle in most cases.
If you really want to build an AK, get a barreled action from someone like Classic Arms. It's the receiver and barrel put together and headspaced, there is no need for a gunsmith or shop. Typically they include some of the other parts as well. I spent more on a machine shop just trying to get the barrel pressed in and headspaced, than what a barreled action would have cost. I learned the hard way that building an AK from parts is expensive. But if you go the barreled action route, it will be much faster, easier and cheaper. I think you can even get it refinished from the company selling them, which will save even more money, especially if you aren't for sure what you are doing.