I don't know if it's a good idea. The 1911 is a pistol that needs fitting during assembly and test fired after final assembley to insure proper function. But if you assembled one and got it working good, it would be worth it if you didn't run into issues.
The kits vary quite a bit in quality and consistency. Essex Arms was a common place to get the frames and slides from back in the day. Some slapped together and some required extensive fitting.
Caspian Arms would be a good place to buy the parts needed to build a gun, but they really are not all too cheap.
I have built a few 1911s, mostly with Caspian components, and great results.
However, it's not like an AR that you snap together. This blog should give you the gist of it (it is lengthy and detailed, which is what you need in this case):
With the profusion of inexpensive, quality 1911s on the market today, there would be little to no savings and a tremendous time investment to try to correctly build a basic 1911.