Most sites that offer wholesale or have a separate warehouse aside from a physical store location (e.g. Snakes At Sunset, Underground Reptiles, SATOO, Big Apple Herp Supply, Reptile Pets Direct, Imperial Reptiles & Exotics, XYZ Reptiles) are going to have animals of questionable quality, mainly because reptiles available in bulk quantities usually cannot be individually tended to without losing a sizable chunk of profit. It's often not possible to tell how animals in a back room of a store are being kept, which means they can be stored in subpar conditions under the semblance of good care presented by a physical store that's open to the public; as long as the public storefront is well-maintained, people will often assume that animals kept elsewhere will be under good care as well, something that can easily be false. Sites with a lot of wild-caught animals often rely on making a quick buck trying to flip cheap imports before they die, which is why they also often try to offer wholesale. While live arrival guarantees are generally a good thing, if their temperature window for the guarantee is relatively narrow (<45F) and they still ship year-round, avoid the site, for nine times out of ten they expect an animal shipped in cold/hot temps to die and don't want to be responsible for replacing or refunding the customer. If the site does not offer a way to freely write reviews and/or they have a social media page where people actively yell at them for shipping dead/dying/sick animals or any negative reviews circulate on public forums or other places, avoid them. It is still important to note that sites like the ones mentioned above will still sell healthy animals, as they still do care about the customers and the animals they sell and will attempt to keep them alive and well to some degree; it's just that they have a lot of unhealthy animals under their care and will try to sell them as well. Websites that have a multitude of rare animals for cheap prices or "too good to be true" offers (may also take on slightly altered or misspelled names of popular sites) are most likely scam sites. Nearly all "major" websites that sell reptiles online are fraudulent in some way and shouldn't be trusted.
Though it isn't a very convenient option, and still isn't the most safe, MorphMarket is similar to a modern-day Ebay (or kind of like Aquabid but without the bidding) where several breeders and/or vendors list and sell their animals; because both the customer and seller have to actively interact to buy/sell an animal, it's a bit more trustworthy as this way there's opportunities to ask questions and form a reasonable opinion on the seller without having to rely on potentially false information; the ability to ask for images and videos of an animal available for purchase to confirm the seller's validity is also another advantage of the site. Confirmed buyers can leave reviews that (as far as I'm aware) the seller cannot directly alter or remove. Then again, unscrupulous sellers still exist and scammers also are on the site (though scammers are usually quickly expunged once reported with evidence), and the user interface isn't the most convenient.
The best way to purchase reptiles is, in my opinion, attending expos and picking out animals in person, or buying animals from people you know firsthand or wholly trust from both experience and word of mouth. It's almost always going to be a gamble when purchasing animals online, which is why I don't do it much (though sometimes it's unavoidable).
When talking about buying reptiles, morality and ethics is a large factor in deciding a seller to buy from; at what point do you consider a breeder/seller to be unethical or not worth buying from? There is no breeder that is unanimously considered good; every person has their flaws and limitations. There are some that treat their breeder animals with significantly less care than they do the offspring they produce; others have a reputation for unscrupulous business practices (The Serpentarium is notable for both these points); a couple breeders actively produce offspring from illegally collected parent animals (some poison dart frog sellers are notable for this; an example of a somewhat common dart frog with very questionable origins is D. tinctorius 'Tumucumaque'), and many willingly breed animals that have health issues (like spider BPs and enigma leopard geckos) for profit. A few breeders/sellers are quite knowledgeable and have lots of experience in keeping and caring for the animals they have, but still tend to gravitate towards negative, sometimes downright dangerous care and recruit questionable employees while still being somewhat honest about the animals they sell (like NERD, for example). Occasionally, there'll be breeders that endorse the wrong products and people, while maintaining good practices themselves. The significant majority of breeders (usually snakes but also reptiles) keep their animals in what many would be considered subpar "enclosures" (like tubs/racks or extremely small spaces), but have healthy animals and aim to keep them that way. Only a very small minority keep all their animals in good enclosures and treat them as they would a cherished pet, but they do not sell a lot of animals, nor are the prices usually cheap.
The list goes on and on, but at what point do you draw the line for whether a seller is worth buying from? At some point there's going to be an animal you want that's only available from the "negative" side of the line; is it worth crossing the boundary to buy it? How much are you willing to sacrifice to care for an animal? How much do you respect the community, and to what point are you willing to shift your views to suit them? At what point is it unethical to breed or purchase certain animals? How much will it worsen the trade if I buy from a bad seller? These are all few of the many headache-inducing rabbit holes of questions that come with being part of the reptile-keeping hobby, and that's partially why I gravitate more towards fish than I do reptiles; the underlying questions are still there, but the keepers seem to make them less of a problem.
