The problem with AE-1 is that there were literally millions of them sold which makes them super easy to find in good condition, and they use the old Canon FL/FD lens mount which was discontinued in the late 1980s and makes the lenses used by AE-1 incompatible with modern EOS/EF-mount cameras.
There were two versions of AE-1 (original intro'd in 1976 and "Program" from 1981),. Both of them are very common in matte chrome finish, more rarely found in a black lacquer finish. The black finish is also more prone to show wear from use (dents, scratches and "brassing"). The matte chrome finish hides flaws and wear better.
Original AE-1 in chrome finish might at best bring $25 to $75, for the camera alone. I've bought them for as little as $10 in good condition. A black body in really nice condition can bring $50 more, but if it shows a lot of wear that will reduce its value.
The later AE-1 "Program" version is also a bit more valuable, with some nice enhancements. The original AE-1 offers manual and aperture priority auto exposure. The AE-1P has those plus an additional program exposure mode. The AE-1P also got an improved, brighter viewfinder and interchangeable focus screens. the original AE-1 can be fitted with a Winder A and is compatible with the later Winder A2, as well. Those provide maybe 2 frame per second film advance. The AE-1P works with those Winders, too, but it also can be used with Motor Drive MA (which also works on the A-1), with approx. 4 or 5 frame per second film advance. In chrome finish the AE-1P might bring $40 to $125... in black finish $50 to $75 more. Again, wear and tear will reduce the value of a black body.
Both AE-1 versions use essentially the same internal shutter and mirror mechanisms, which is prone to developing "shutter squeal" when the camera sits unused for a long time. In spite of what it's called, this it is actually part of the mirror lifting mechanism that causes the noise. It's due to lubrication that's dried up and no longer doing its job. Advance the shutter wind lever and press the shutter release button, to see if the camera exhibits this problem (battery required, see below). It will be pretty obvious from the noise if the camera has shutter squeal.
I know for certain the AE-1 Program and am pretty sure the original AE-1 are "battery dependent". In other words, they will not function without a battery installed. This is due to the micro-processor controlled shutter. That makes for more accurate shutter speeds, but no longer has fully mechanical "clock work" that can operate without a battery. As a result, to test the camera for shutter squeal will require purchasing a battery, if you don't already have one. The good news is that the AE-1 models doesn't use the no-longer-available mercury cells that many other SLRs of that time used. Both AE-1 use commonly available six volt 4SR44 (silver oxide) or 4LR44 (lithium) batteries. It also an use a single PX28A (alkaline) battery. Alternatively, they also can be powered by a stack of four of the smaller, 1.5 volt SR44 or LR44 batteries (which are a little more difficult to install). There are a couple other batteries that also can be used, but those are the most commonly found. If you don't have one, I recommend you get a battery and install it in the camera to test it for function. It's not a big cost and buyers will appreciate that the camera has passed basic tests. (Remove the battery when done testing.)
To install the battery requires you first remove the grip (assuming it's still on the camera.... many were removed and lost). It's held in place by a simple screw that has an oversize slot so a coin can be used to loosen it. With the grip off the camera, the little door covering the battery compartment can be accessed. It has a little latch. Gently press that to release and open the door (it's made of plastic, so handle with some care). Note: Last time I looked, replacements were available for both the grip and the little door covering the battery compartment... but if the originals are still in place and good, they are probably better quality than the "clones" now being made.
Shutter squeal actually isn't a big deal, but it devalues the camera to a lot of buyers. It's possible to fix it with a tiny drop of light oil placed in just the right place ("sewing machine" oil works fine). However, it would be better if the camera were given a proper "CLA" or "clean, lube and adjust", which a 30+ year old camera probably needs anyway. There's also good chance the camera needs new light seals installed. Those wear out or get brittle and crumble from age. Having a CLA and new seals installed will likely cost around $150 or more. I'm not suggesting you have this work done, though, because you won't recoup your money. A fully tuned up and properly working AE-1 just isn't going to sell for enough to recover what you'd spend. Even in top working condition, they are unlikely to bring significantly more unless the camera is fitted with a high end lens.
If you have a manual with the camera, great! If not and you want one, it can be downloaded from
https://www.butkus.org/chinon/canon.htm (different manual, depending upon whether it's the original AE-1 or the AE-1 Program). Manuals are free there, but donations are appreciated.
Unfortunately, the lenses and flash with the camera sound as if they are all "consumer grade" third party and nothing special, which usually sell pretty cheap on the used market.... particularly in the old FL/FD mount that isn't compatible with modern Canon EOS/EF mount (can be adapted for use on the Canon mirrorless). I wouldn't expect to get more than $10 or $15 apiece them. If you search eBay for "sold" AE-1 you will find most with more favorable selling prices are fitted with Canon 50mm FD"n" f/1.4 or f/1.8 lenses, which are more valuable than third party lenses.