First day of a group project and one of your group members utters the immortal phrase: "what's a get hub?"

Running a small company. All of us work from home. I am a designer and coder in one person, but now mostly taking care of cash flow, work done etc., while I have my dear girlfriend as only designer and an old friend as only front/backend developer. We are doing mainly small presentation websites on drupal, and a lot of webdesign.

Now I want to ask more experienced devs here. As the "main guy" I am responsible for everything running smooth with clients, money flow etc. But I am constantly running in a serious problem with my developer.
He most of the time gets the job done. But it is as fucked as possible. It looks good at the first view, but when you check the code... Oh god. Not only once he wrote me he did the job and when I checked it, it was like 50 percent done and rest was let untouched. He is using the oldest approaches in css as possible. Most of the time setting fixed widths even when I told him not to do so. Thing is, he knows how to do it properly, but he rather set the fixed width for all the devices than write something more scalable (imagine fixed width buttons, now imagine a website with 5 translations and now imagine how it behaves on mobile phones).

I want to be in a state where my dev writes me he did the job and I can INSTANTLY pass the changes to client with a trust of good done work. Without checking constantly all the work after him. Or it is normal and it works like that everywhere?

As to mention, I think he is pretty good paid and this is not money problem. It even does not look like he is demotivated or anything. When I speak to him it looks more like he is lazy to learn new things and lazy to do a good work. What would you suggest? Thanks