Recommendation: don't do it to save money, but because you want the pleasure of doing one for the sake of doing it.
Second recommendation: buy the Kuhnhausen 1911 manuals-both volume I and volume II. Don't try to build one until you have read them and understand what they say [$80 for both, probably, if you find a discount].
Third recommendation: invest in the proper tools/stones. This cost me around$200 in tools, beyond what I had, and that doesn't count my attempt at checkering the front strap.
Fourth recommendation: blueprint the final goal you wish to obtain. Do you want a 'carry gun'? Do you want a competition gun? What type: IDPA? Bullseye? Do you want a true 1911, a 1911A1, or a modified 1911a1 [beavertail, commander hammer, etc]. Do you want a 5" GI, a 4.25" Commander? A 4.25"-4" CCO? An Officers' size? or smaller? Do you want flat/arched or bob-tailed MSH? Do you want bull-barrel or bushing barrel? Do you want ramped barrel or swinging link? Why? Understand why you want it before you proceed. Understand the differences before you commit the money.
Research part names and decide what you want to use. General recommendations are ok, and there are a LOT of other good companies. Basic makers of most parts: EGW [evolution gun works], Ed Brown, Wilson Combat, Nighthawk Custom, Cylinder & Slide, KART, etc. [I am not slighting anyone: the list could be days long and still miss someone.]
Factor in the price of messing up at least two parts: sear and barrel bushing, for example, might require a 'do-over'.
Decide if you want basic iron sights, nightsights, or adjustable sights. Find the make/model you want and price them.
IF you are going for a beavertail grip safety: do you want a .250 cut, a JEM .250 cut, a Wilson/Caspian cut or a .220 cut? Why?
Price the cost of the finish you are thinking of: blued? CeraKote, CeraPlate, NP3+, HardChromed, Melonite, Nickel, Parkerized, etc.
NOW, pick the maker of the frame/slide you wish to use. Do you care if the frame is forged v Cast Steel? Do you want an aluminum frame? Stainless or 4140-type steel?
Now that you have these details worked out, decide if you want to actually fit the slide to the frame [extra tools/parts/time], or have THIS done for you. Caspian, for example, will fit the slide to the frame, as long as both are their products. For a charge, but it can be done. However, it may not be as 'tight' of a fit as you wish. [how tight do you want it to fit, and why?]
OK, that is the research and self-discovery for you. Be realistic: exactly HOW skilled with tools ARE you? This is a firearm. If it is a defensive firearm [nightstand or defensive], and not a firing-range only toy, you better be darned sure of your technical expertise: that is the only thing preventing a double-shot unintentionally.
Read up on all of this at 1911 forums dot com.
OK, if you have done this and are SURE you want to do it, take one LAST look at the cost of EVERYTHING: from tools, stones, files, to EVERY part, and the cost of having it all finished for you. Do not forget springs and grips in this cost.
Got a figure? NOW, take that figure and take one last look at higher-end 1911s: Wilsons, Upper-end Springfield, Nighthawk, Ed Brown, etc.
If $ is the issue, you might find that you can buy one already done to specs you will be happy with for less than the amount you just spent.
Keep in mind that the tool costs are to be counted toward the cost of your 1911, unless you build more than one: then spread tool costs between them.
NOW, I will say this: I REALLY enjoyed building the 3 1911s I have worked up. One is a 5" full-'race ready' Caspian, set up for bullseye type range-only use. I haven't had it professionally refinished yet: it is wearing an OXPHO-Blue cream finish. Here is a picture:
Custom Caspians Mine is post #433. It has a 3.5# trigger break.
The second one I built is more of a defensive carry 5" 1911, with a trigger break closer to 4.75#s. It is based on a Sistema frame and a Armscorp slide.
The third one is almost finished, and is a 4.25 CCO, based on a RIA frame/slide. No pics until done.
I really enjoy doing this, but I admit: it is EXPENSIVE!
It does NOT save money.
My Caspian has all ed brown parts, except C&S trigger, and it cost me around $1200 so far, without a final finish on it. A SA Trophy match would cost around that much, with checkered front strap. A Kimber Gold Match is around the same price, and a Team Gold Match is around $1800.
When I am done, I expect the finish to run me close to $400, counting shipping both ways. I am into mine for over $1500, but probably couldn't sell it for more than $1100 at that point.
PLAN, PLAN, PLAN. It isn't hard: but it IS time consuming, you have to be patient, and you have to be willing to spend more than the final product might be worth. I didn't realize that I REALLY needed a drill press to do the bushing 'right'. Table-top for $180 and I am set for life, as I can use it on other projects, but it was another $180.
That said, you could build up a different frame and have $1800 into a gun that might be sold by Wilson for $3000.
It all depends on what YOU want it for.
I will say this: it seems like a waste to buy all the tools and then just build a basic 'g.i.-spec' 1911. No grip safety fitting, or other parts. Simple. And I am just as happy shooting a Springfield GI for the cost of the frame and slide, fit, for a home build.
Good luck: keep us posted!
All the others responded as I typed. Good ideas everyone!