The crux of my argument is: If you are building a track/fixed bike from scratch or just a handful of ingredients, start with a good track or fixed specific frame.
Track bikes and conversions are very different beasts. If you want a track bike, go buy a new or used track bike.
That being said, there are plenty of perfectly functional bikes in dumpsters and thrift stores that need nothing more than a good scrubbing and some grease and often new rubber, bearings and a chain. These same bikes can be fixed with the addition of a track cog and some loctite if that strikes your fancy.
A decent thiftstore or dumpster bike + $75 + 3 hrs = fun, functional transportation that costs a few pennies per mile to operate. I can't imagine why anyone would counsel against this. If you want to ride fixed on a limited budget this option makes the most sense, especially if you have some tools or access to them through a co-op.
If you want to help out the noobs, volunteer at a co-op or hold a clinic in your backyard.