are you going to make a soft plastics mold or lead mold?
i get the best price from my employer, plus i'm able to use payroll deduction so i dont have to pay for it right away! one thought though, i dont know if i would use alum. or brass for a mold, as it would warp after a few uses caused from the heat. i would go with a soft steel like 4140, easy to machine, plus stronger. you will want to hinge it also, you could pin it but after pouring, the mold would expand and sieze the pins, you may have to "help" break the mold apart. this could cause damage. i'm sure some one here could elaborate more on the preferred mold material. if you have access to any vertical mills at work at all, i would go that route also. i just go in on my day off to do personal machining. wouldnt be hard to program a simple mold. and better yet if you have access to cam software, you can make a solid model and really get creative! hope this helped!