How long is the normal wait for eggs when you buy older pullets?

I just recently (2 weeks ago) bought 5 NHR pullets from a hatchery/chicken farm in CT. Well I bought them from my neighbor who went and got 20 of them, 5 being for me. He didn't tell me how old they are. They are huge compared to my 8 week old chicks and look full grown or nearly there. How old are the normally sold ready to lay pullets? I'm just trying to figure out how long of a wait I'm in for before I find that ever special first egg...

 

I do hope you have them separated as far away from your 8 week old as possible?

I have to admit that I didn't seperate the birds like I NOW know I should have. As much as I knew that I should have quarentined if I bought from say joe shmoe's flock down the road, I figured, dumbly, that I was safe because they came from a locally well know hatchery with a great reputation. I now know MUCH differently. You live, you learn right? I have been watching them like hawks for any signs of anything so lets just hope and pray that I didn't sign a death sentance for my flock with these girls.
The other thing I wonder with quarentining (didn't spell that right I don't think) is when you say "as far as possible" whats the minimum space apart we're talking? I'd like to know for down the road because I only have one really good (largeish) area for my chickens and ducks due to my having horrible neighbors who are sneaky and deceptive and spy-like, not to mention vulgar and hate all animals and children! So I don't have many different places to quarentine a bunch of new birds, should I ever do this again (which I doubt)... I could make a quentine area if I should ever need one about 100-200 feet away from my current coop, is that too close?

I think I'll stick with day old chicks from here on out just to be safe.. Do you also have to quarentine chicks that you've hatched yourself I wonder?

Anyway, Thanks Miss Prissy for the response. I rushed into this whole chicken thing like a kid in a candy store at first and I certainly am learning from this forum!​

 

Yeah I honestly think I will follow suit and not bring any other adults in again...
I only got these girls because I was always buying eggs from the neighbor who "sold" them to me and we got to talking about him needing new birds because his flock got taken out by foxes, so he was like "You're going to be waiting forever with those chicks you've got, when you could have eggs for your family in just a few weeks with these older ones" at the time it sounded like a great idea... I didn't second guess him because he's been buying from them for over 20 years and at one point had almost 1000 chickens and was running a business so I just sort of trusted his judgement without question. There lies my first mistake. Now I'm just hoping I got lucky with the new chicken roulette and didn't bring anything nasty in and I certainly have learned since then.
I even have one of my 8 week old marans right now who have been coughing and sneezing on and off for 3 days with absolutely no other symptoms, the sneezing/coughing/clearing throat noise comes in short bursts, sometimes only 2-3 times a day. She's the only one and I have her very isolated in a large cat carrier away from my coop and my brooders. She's also making differrent noises, like big chicken bhoking all of a sudden... I have no idea what's up with her but I'm watching it VERY close, she's eating and drinking great, poo is normal, is not lethargic at all. I posted about her on the illness/emergency/cure area a couple days ago but haven't heard from anyone.

Anyway, thanks again!