you can find lots of Siamese cats in shelters unless you're just dead set on having papers. my first one was 2 years old when I got him, and had obviously been someone's pet. he had zero bad habits or behaviors, I can't believe someone dumped him. one day I accidentally shut him in the bathroom all day when I left for work (because there was a full-length mirror on it, but I usually remembered to open it) and he did not even pee in the tub--he held it!! I couldn't believe it and wouldn't have been upset if he gone pee or poo anywhere in the bathroom because it was my fault. he was a beautiful seal point, and lived to be 17 until '06. he did have horrible stomatitis for which I ended up having all his teeth removed, and sometimes I have wondered if whoever owned him knew that and just didn't feel like spending any more money on it. if they got him from a breeder, he had slightly crossed eyes and a crook in his tail, so he would have definitely been pet quality. he had been declawed and I ended up fixing one of his toes where the claw was growing back inside his paw, but that's a side effect of declawing and he wasn't born that way.
the second and third are both lilac points. I bought the second one after Coda passed and the third was from DFL, originally to replace Baci lol. the one I bought was adorable until he was 11 months old and started to pee in my bed. he also incurred a lot of vet bills in even the first month (not a fault of the breeder, I don't think though). he has the most skittish personality of all three, but he is getting more relaxed. he has no bad traits typically thought of as Siamese, except he has a weird loose end on his tail, you can't see it but you can feel it. the tip feels like it isn't connected to the rest.
the third I got from the DFL, originally to replace the bed-wetter but Mr. Pee Body stopped so I have three cats.
he has extreme vertical strabismus, which is just that his eyes look like they're rolling back in his head sometimes. I don't think he has bad gums though, because he's three and the vet said he doesn't even need his teeth cleaned yet.
you should be able to get a pet quality (as opposed to show) for $350 (sometimes even less if it's a grown cat) depending on where you live. queens should be retired anywhere from three to five years, but she should be spayed already. a reputable breeder would not sell you a queen they retired still intact because some people will just start breeding them again. it will be much easier for you to buy a cat if you make it clear that you will not be attempting to breed. sometimes there's just a contract for you to spay or neuter, but if the kitten is already altered, that will add to the price at least $250. it isn't better or worse to buy an intact kitten, it just depends on how much you want to pay.
go to the breeder's house and look for all the things mentioned. they should be happy for you to come. if they aren't, bad sign. if one or two things is a violation, you decide if you want to risk it. Siamese kitties are very vocal. I mean, VERY lol. all three of mine have had bizarre meowing habits, so if that bothers you, don't get one. the middle one of mine does this cross between a baby crying and gargling. the vet knows and there's nothing wrong with him, he's just annoying when he wants to play in the middle of the night. to be honest, I don't even hear it. (the only cat whose meowing bothers me is my old cat with some health problems, and that's because hers changed to kind of an ugly meow. it's also very high-pitched compared to the others.)
Siamese cats are a lot of fun though. I actually think they're sort of clingier than other cats, so hopefully you can spend a fair amount of time with him/her.
Siamese cats are so much more common than some others that they might just want references, but sometimes breeders want to visit your home, and also want assurance that you don't smoke. ask them what they are being fed, what kind of litter, etc., things that you'll want to know when you take them home. some of them will just tell you, others don't.