Just curious, why not go with a 7075 lower? I'm considering the 5D jig kit because I already have a router. IIRC they even recommend various brand routers for folk who want to buy the bare minimum tools to make a lower.
The way I see it, after you make a couple of lowers, either sell it off to recoup some cash, or have a buddy or two donate to the purchase so they can make a couple of lowers too.
I have the first gen 5d jig. Works great. The newer model looks even better with hardened bushings a better designed endmill , and shopvac port to help clear chips away. I've completed 6 lowers with it. I did chip an endmill , completely my fault though. I would recommend brand new drill bits for each lower or at the very least freshly sharpened bits.