This is the bare minimum that you can do to a bike such that you can get on it and pedal. We've got one brake and one speed. In fact, I've done less - I've built bikes to evaluate with no brakes and no chain. But in this case, I wanted to ride and turn it to see how this bar fits.
The fork is clearly not right, and there's no star nut in it, so the headset is loose. And that's one of my favourite single speed hacks on the rear derailleur - run a brake cable through the barrel adjuster so you can fine tune it over whatever gear you want.
Next level would be Just Make it Go. Everything is buttoned down and works properly - mostly. It's just a higher level of evaluation. It doesn't shift quite right, maybe the brakes drag a little, probably because the wheels need to be trued.
From there it's Seller Level. Everything is working properly to the level that the buyer could jump on and ride it home.
Finally we have My Bike. At this level we're overhauling all the bearings, replacing all the cables, cutting the housings just a few millimeters at a time to get the length perfect. I'm going for flawless in mechanical condition and appearance.