An idea to make profit

So you want a new idea on how to make profit?  I wouldn't recommend the unusual market, but how else can you make keys fast?

I like high-value stranges and promos trading.  Basically, you buy high-value stranges worth a lot for 1-4 keys under their value, depending on their value and on demand.  Then you flip them for full value.  It's criminally easy.  Have an example:

http://www.tf2outpost.com/trade/3493543

That post made me dozens of keys.  Just buy them for low, and immediately repost them for full value.  It's an easy and great way to profit.