well, building an AR is not real hard. if you can install batteries in flashlights or toys you should have no problem.
the hard part is in the current times finding AR parts is very hard. even harder if you do not want to pay a premium. a year ago you could of built a good AR for 800. now your probly looking at 1500.. if you can find the parts. they are out there just takes alot of searching.
If I were you, I would not attempt to build the upper receiver yourself if you don't already have the tools, a workbench, and a vise but assembling a lower only requires a roll pin punch set and hammer.
I assembled an AR lower for the first time last Friday using a Colt stripped lower and Colt parts kit because I wanted to do it myself so I know how. All I needed to figure out what parts went where was a diagram available on the internet that showed all the lower parts. I substituted a MagPul CTR stock and MagPul MOE grip, but it really was remarkably easy.
I used a Grace roll pin punch set, a bit of duct tape to prevent any marring marks on the lower from the installation of the bolt release roll pin, a piece of Barilla spaghetti to hold the bolt release in place to punch the roll pin through, a small hammer, and a credit card for installation of the captive receiver pins, and locktite for the castle nut.
The front roll pin is annoying to assemble, but the rest of the assembly was easy. It took about 30 minutes at a very leisurely pace.
I have a stock wrench for cranking on castle nuts, but I opted to locktite (use blue not red) my castle nut in place. You'll need a degreaser or chlorinated solvent like GunScrubber to do that. The mil-spec staking job is not necessary for something you're not taking to Afghanistan.
I built AM/FM radios as a child and thought that was relatively simple, but assembling AR components is honestly pretty dummy proof. That said, make sure you read about how to properly torque the barrel extension if you opt to assemble the upper and use a torque wrench.
As far as costs are concerned, AR components are overpriced these days.
Do you have 556 to shoot through it once you assemble your new toy?
My build is one of the stickies in the AR-15 subforum. It was really easy and was the first experience I ever had in gunsmithing. It's really easy enough that you can't even call it gunsmithing. It is really just LEGOS.
You're about 4 months late, though, sorry to say. On the list of parts you will have a rough time finding are: a lower parts kit, a bolt and carrier group, maybe even a complete upper.
Perhaps you should just get a list together and start trolling the used sites for parts. Some AR parts are coming out of the woodwork from people with extras who want to make some extra money during this time. You'll able to find parts on the classifieds that you'll have a really hard time finding new on the normal retail websites.
As far as cost...you used to be able to build your own for $800-1000. Not anymore. $1500? Skies the limit, I suppose.
Here is my take on the DIY AR15: It is not for everyone. However if you are slightly technically inclined, you can probably do it. However if you aren't comfortable around tools, don't try.
If you think you are going to save gobs of money, you are wrong. The investment in tooling will make your first build cost more than if you were to buy retail. However if you plan to build more or do alot of tinkering later on, the tools will eventually pay for themselves.
The best reason to build a custom AR is, well, because it;s custom. It's exactly how you want it to be. Almost all of us with the black rifle disease have a parts box of items we took off, swapped out, or upgraded... left over parts. If you start with a custom kit your parts box is usually smaller because you got most of the parts you wanted the first time.
You still can build a custom AR for less than $800 (plus optic) if you can find a lower less than $200. I know places where you can buy complete kits for about $600. Everything you need, except the lower, to build your AR. Not at all custom, but it's a great place for beginners because you are sure you haven't forgotten anything.
Even before Sandy Hook and what happened to prices since, I wouldn't recommend building a custom AR for less than $1k budget. It just wasn't worth the time and effort in my opinion. In my mind the reason for a custom build is to build something nice. Anything less than 1k, pre sandy hook, you could get equal off the shelf for less. But once you start looking at AR rifles $1k plus retail prices, you usually can save some money by building custom. I reread this paragraph and it is a little confusing, so I hope it makes sense. Basically the summary is if you have a big budget, go custom all the way. Otherwise buy something off the shelf.
Design is the biggest factor in my opinion however. What I see happening now because of parts shortages, guys are just buying WHATEVER they can find. This will yield less than optimal results if you ask me. Really have to look at alot when you are designing your build before you even start buying parts. Sure many of us can build complete AR's just from the parts we have in our boxes, and in most cases they will work, just might not work great.
Understand first what you want to build, and why you want to build it. Home defense? 3 gun shooting? hunting? bench rest shooting? Then research which parts are appropriate. Then start scouting out those parts and start placing back orders with reputable retailers, nor opportunistic price gougers. Parts are trickling in slowly. If you have patience you'll get the EXACT AR you want.
If you buy a lower that was registered by the factory when built as a rifle lower, then you have a rifle lower receiver.
If you buy a lower that was registered by the factory when built as a pistol lower, then you have a pistol lower receiver. You are not yet 21, so you can't purchase a pistol from a FFL.
If the lower was transferred at any point in time as a rifle lower receiver or was not originally built and registered as a pistol lower receiver, then you have a rifle lower receiver. If you first put a rifle stock on a pistol lower before putting a pistol stock (or pistol buffer tube) on a lower, then you have a rifle lower receiver. That's pure BATFE firearms magic there, but that's BATFE's opinion on the matter.
From what I understand from what the BATFE Firearms Technology Branch has opined on this matter, having a pistol lower and converting it to a rifle format or from a rifle back to a pistol is legal. It is not legal to convert a rifle lower to a pistol format. You would then be in constructive possession of a short barreled rifle (even if you don't have the parts to convert your pistol back to a rifle). The act of converting a rifle lower to a pistol format is considered making a short barrel rifle.
Additionally, you must keep the pistol AR upper mounted to a pistol AR lower and not have additional AR rifle lowers in your possession with no rifle uppers attached to them. This is considered constructive possession of a short barreled rifle.
If all of that was not convoluted enough, there's no actual statutory or codified law (that I know of) regarding the matter of what constitutes a rifle constructed from a pistol, just whatever BATFE FTB decides is the law.
To regurgitate, a pistol lower is a pistol lower if originally built and registered as a pistol lower. A rifle lower is a rifle lower if originally built and registered as a rifle lower. You can't purchase a pistol or a short barreled rifle (or any other Title II firearm) from a FFL until you are 21.
My advice is to buy an upper and lower parts kit, wait until you are 21 (hopefully prices will return to sane levels by then), and then buy a lower to avoid all possibility of the stripped lower receiver being considered a pistol.
For example, no Colt lower receiver is considered a pistol lower receiver. All lower receivers built by Colt are considered rifle lower receivers, whether stripped of all components or not because they were registered by the factory as rifle lower receivers.