Build one
For $700 I would buy a fitted frame and slide, perhaps with a prefit barrel and bushing. Then buy hammer, trigger, grip safety, mainspring housing etc.
You would learn how it operates and you would get something that is set up the way you want. There are some kits that have the hard stuff already done, things that take special tools to install certain parts.
If you get a alloy or stainless frame, you don't have to worry about bluing.
This assumes you have a idea now of what you want.
I'm thinking of setting up a dedicated frame for my .22 conversion unit. I came up with just under $500 without a slide or barrel, by pricing stuff from the Midway catalog. There are many places to find frames, parts etc.
For now buy some shop manuals and videos etc and learn about the 1911. This will be helpfull even if you go buy a completed pistol.