Building a 1911 is much, much, much different than building an AR15, requiring specialized tools (especially a milling machine) and specialized knowledge about the gun itself and machining processes. It's a lot more complicated than watching some vidoes and parts out of a brownell's catalog.
If you are a machinist by trade, you might be able to do a decent job at it.
I do my own sear/hammer work, extractor tuning, mag catch fitting, safety lock fitting, and some other misc things like sight changes if they are not too hard, but then I've been to the 3 day armorer class and I have probably over $1k in 1911-specific tools.
Closest you might be able to come to building your own 1911 might be to buy a gunsmith kit (offered by Caspian, STI, SVI), where the slide/frame/barrel/slide stop/grip safety/sight cuts are already done, and then to buy a pre-fitted hammer/trigger/sear kit.
Even then, there is a lot of things that can go wrong on you, and finished product will not be nearly as nice as something you can buy off the shelf, or have made for you.
Many 1911 parts are advertised as "drop-in", or requiring "minor fitting". In both cases, you'll find that not to be necessarily so.
If you really want to do it, check out the cylinder and slide homepage. Bill Laughridge offers classes on how to build these guns.
For some good basic info on choosing a base gun, check out www.signaturegrade.com
I really suggest you either find a good smith (I recommend Evolution Gun Works, and Cylinder and Slide - but there are many more) and consult them what you want (rather than buying a gun and then contacting them), or simply buying either a Les Baer, Rock River, or Nighthawk Custom.
FWIW, my $3200 custom 1911 based on a SA Mil Spec is not quite as nice as my $1800 Les Baer Premier II with the 1.5" guarantee, primarily due to faults in the base gun. I would not build on a mil spec again, I'd use a Colt new series 70.
SF