Regarding Autoweapons.com, it was splashed all over the internet gun boards at the time (sometime last year). Long story short, one of the principals was arrested and accused of fraudulently acquiring post-sample MG's in order to chop them into parts kits.
"Entry level" machine guns are still under $4000. I realize, it's still a wad of cash, but it's not like we're talking the $25k necessary for an M16 these days.
I saw a Chauchat go for $1600 or so on Gun Broker a couple months ago (granted, it's a Chauchat, but still it's transferable), and spitfires are also often in the ~$3,000 range. Macs can still be found on occasion around $4k.
The best thing to suggest is to save your money up so you have it all ready to go, and then watch sites such as arms list or sturm like a hawk. "Steal-of-a-deal" guns DO show up there, but you have to be *FAST* (often, well-priced MG's will be sold in under an hour) and have cash in hand.