Dave,

It depends on what you want to cut and figuring what you might want to cut as well. What area do you have for the machine (remember you want to be able to get at least two sides of it easily)? Also what skills do you have and equipment? Just saving money during your design time can add to what you can spend on the machine. Also you can use the build logs and forum to hash out what will work best for you.

If you are doing this on your own I would strongly suggest a grade one square to help insure everything is square which a grade one will do for most folks (IF you want really square go to grade 00 but the price can bite).

Also you need to look at software and purpose, why are you building it? That will affect design, materials and tooling. So while it might seem like a mountain, slow down and take the time and you will be seriously surprised at what you can do with a little bit of help. Unless you are a business that needs this yesterday or to further your production ability and than you might want to look at the buying options, but that road can get expensive fast.

-Michael