Fixie for 200$

IMO, $200 is probably a tough price point to achieve if you want a new bike in most parts of the World ... heck, you could easily spend $200 on just a set of "Track" hubs.

However, if you can DIY, you can certainly buy a used, vintage bike & convert it for use as a Fixie-or-SS for under $200.

Others have suggested otherwise, but I will tell you that CHAINLINE matters ...

• in addition to resistance, or lack of
  
• you need to be concerned with the chain staying engaged or crawling off the teeth
  

and, a good chainline ensures a minimum amount of resistance and that the chain will stay engaged.

If the vintage bike has a Freewheel which you replace with either a BMX Freewheel or a Track Cog, you will want to redish the rear wheel ...

If the bike has a Freehub & uses a cassette, then you can simply use spacers to line up the cog.

• you can cut "spacers" from appropriately sized PVC tubing
  

BTW. I've seen Fixies for just over $200 + shipping on eBay. They are certainly good-enough for most riders for most situations ... the hub quality & BB quality are unknown, however ... et cetera.

I seen Fixies on the floor at Walmart during the Xmas season. They were branded Mongoose and sold for around 119.00. I see quite a few of these riding around in the city close by. IMO if you have 200.00 this is a good bike to jump onto. You will have enough coin leftover to get yourself a helmet and roadside repair kit. Fixie components are cheap enough so if you need to replace a wheel or crank along the way it wont set you back to far.
From what I can see locally on CL most of the fixies selling used here are junk pieced together from disposed bikes.