nah Troy, he can do it. M-16 is that price, AR converted receiver can be had for that.
Here is how you find one fast. Go post on Bowers on the NFA ad board:
WTB: AR RR $5500 or less, good condition. Have cash.
you'll be saturated with sellers, check over their deals, haggle, and select the best.
Also, consider a DIAS, they can be had for around $4-4500.