My new job requires that I run a 64 bit Windows program on an Intel laptop. I don't want to buy a Windows machine, I'd prefer to run Windows on top of VMWare, Parallels, or Boot Camp. It just has to be Intel, not Apple Silicon.
While I am empathetic to your plight, buying an Intel Mac solely to run Windows stuff is about to not be the best idea. For one, Boot Camp doesn't directly support Windows 11; nor has Apple enabled TPM 2.0. And, as things stand, Windows 10 is supported, but we're just two years and change away from its expiration date.
For what it's worth, I do have an Intel 16-inch MacBook Pro set aside for the exact same purposes, but the goal is to eventually limit that to virtualizing older Intel macOS releases and to have Windows virtualization needs handled by Windows machines.
So are there any Intel MacBooks out in the channel, anywhere? A friend of mine bought a 5 year old iMac from B&H, still new in the factory sealed box, and another friend picked up a 3 year old Mini just a week ago, but I've been searching and can't find any new or Apple refurb Intel MacBook/Pro/Air anywhere.
I keep an eye on stock of Intel 16-inch MacBook Pros in Apple's "Apple Certified Refurbished Mac" section of their online store, which seems to fluctuate even two years following discontinuation. Last I checked, I saw two models; one of which was way beefier than anyone would realistically have need for in an Intel Mac and the second one was 100% maxed out on everything except the processor and graphics (so, 8TB SSD, 64GB of RAM; 6-core 9th Gen i7; and 5500 with 8GB VRAM) for about $1000 more.
You will occasionally see the 2020 4-port 13-inch MacBook Pro, but I'm finding that's starting to trail off (incidentally, while being the best Intel 13-inch MacBook Pro that Apple released in terms of performance, it's still a horrible value proposition as one's "absolutely necessary final Intel Mac"). You used to see the (Intel) 2020 2-port 13-inch MacBook Pro on there, but that trailed off a while ago (probably because relative to the other final Intel models of MacBook Pro, that one was only on sale for 6 months compared to the 23 months of the Intel 16-inch MacBook Pro and the 17 months of the 4-port 13-inch).
OWC had a massive 4th of July sale on both Intel 16-inch MacBook Pros and 2020 4-port 13-inch MacBook Pros. Most were used but in good condition, if I recall. Not sure if they still have the latter; but I did check yesterday and they had quite a few of the former.
I would STRONGLY caution against using any Intel MacBook Air. The 2015/17 models are too old and can't go past either macOS Monterey nor Windows 10, and the 2018-2020 models were some of the worst Macs Apple has ever made (underpowered and overheating with laughably flawed thermal solutions).
I really don't want to go the eBay / CL route either, due to the risk of fraud.
There are a lot of buyer protections in eBay that will actually help safeguard against fraud by seller. I know this because, as a seller, I've had a buyer use them to screw me over in the past. It's quite safe to buy something on eBay. Craigslist is obviously less so.
Where buying an Intel Mac, particularly one with the T2 Security Chip (which pretty much any Mac you ought to be considering would have), becomes a real pain (and where you could easily run into the kind of trouble that eBay might be ill-equipped to handle) is with Activation Lock.
Where Activation Lock prevents an iPhone or iPad from making it past the setup assistant with iOS/iPadOS, it's a little different with macOS and Macs.
With Apple Silicon Macs, this pretty much works the same as with iOS and iPadOS; a user pretty much can't wipe the drive and/or complete an Apple Configurator 2 restore without entering the credentials of the user that had "Find my Mac" turned on prior to the wipe. It's also pretty easy for someone to wipe their Apple Silicon Mac and encounter this in the natural process of getting the Mac ready for sale.
However, with Intel Macs with the T2 chip, Activation Lock isn't enforcing macOS in this fashion, but rather bridgeOS - the OS that the T2 chip itself runs. A user could wipe a Mac with Activation Lock enabled several times before even noticing that Activation Lock was still enabled and tied to a previous user.
I have run into this problem enough times when buying T2 Intel Macs that I swear I do not want to buy another T2 Intel Mac used (and also want to limit how many I'm actively using in my arsenal to a single one). I do not feel this way about Apple Silicon Macs and Activation Lock.
Apple does make this problem easier to avoid with Ventura's version of the "'Erase all Content and Settings' Assistant", but that requires that (a) the person wiping the Mac have been running Ventura all along, and (b) has access to the Apple ID credentials that turned on "Find My Mac"/Activation Lock to begin with (which itself is generally not so bad so long as you are buying from the original owner).
So, in short, yeah, definitely be wary of Craigslist, and definitely be wary of going to eBay for any T2 MacBook Pro (which honestly is what you ought to be looking for if you absolutely need your Windows PC to also be an Intel Mac). Though, honestly, I'd give thought to just getting a Windows PC for your Windows needs. Feel free to PM me if you want a list of recommendations that won't suck.