Introducing second rat?

We are new rat owners as of last night. We went to pick up our friend fully expecting to come home with a pair of females (one for my daughter's 9th birthday and one for my son, 13). Everything I have read says that a single rat will be too lonely. However, the store clerk informed us that if we wanted 2 rats we should consider 2 cages as the rats, if housed together, would bond to each other and therefore, not as much with us. Now I am reconsidering her advice and I am wondering if I should go purchase another female today. Would I be likely to still have intro issues or because they are from the same litter(?) and have only been separated for less than 24 hours they will be fine to put together right away.

No go ASAP! The sooner you get the second rat (same gender) the easier the intro. They would be fine at a young age even if not from the same litter. Its rare that young rats have intro problems, its the older ones who have established their place that have a bigger problem. The rats will bond with everyone at their own pace regardless of group number. Its the effort you put in to bonding with them.
I find groups of 2 are a great start because sometimes one wants to hang back in the cage and you get one on one time with one of them or both will come out and you get to see just how special and individual each one is.
As long as they are the same gender you should have no trouble getting them together today. You don't want to mix the genders now as they will breed and you will have more then just a pair!

I have six rats and they all live in the same cage. They are definitely happier with ratty company. As it has been said, young rats are easy to introduce, and if the girls are from the same group at the store, then they already know each other.
I would encourage you to double check their sexes before putting them together. Hold them up and compare parts. It is pretty obvious if they are different. Some people have been told their rat is one sex, only to find out it was the opposite.
They will bond with you regardless of their living situation. It comes down to their personalities and how you handle them. It would be cruel and selfish to keep a rat lonely so that they would crave your company. Treat them with love and yummy food, and they will quickly be at the cage door any time you go by.

Thank you for your help. We will definitely go get another tonight. My son is very excited. If there are no females left from the same group and I must go to a different store should I just look for a rat that is about the same size? It seems like different stores had different sizes/ages. When you say young rats, around what age do you need to be more cautious. We watched the group for quite some time and chose the rat that was watching us and seemed more in tune to us than the very active scurrying rats. I'm assuming this is what I should look for again tonight? Thanks again for your input!

Usually if they are only about have their adult size your intros should be easy. Honestly in my personal experience it was easy with rats that were as old as 6 months of age. You should be fine getting them someplace else. Have you checked to see if their is a rat rescue near you? Sometimes they have very young rats come in, and it would be a great place for you to get more accurate advice.

With this one being (I assume) young it should be easy to introduce even a slightly older rat. Just keep the gender the same! Lol can't stress that enough. Look for nipples only girls have nipples

If all rats are under 12 weeks of age (babies) then intros are easy.
You just put them together because babies see a new rat as a new playmate.
Just make sure they are the same sex (girls have 12 nipples, boys just have a belly button, and boys have testicles).

As others said, rats need to live with at least one other rat.
Single rats are very lonely, can become afraid of people, withdrawn, depressed, etc
Rats who live with other rats are much happier and social.
Here is a good video
[ame]http://www.youtube.com/watch?v=cDy3bMRuobE&feature=related[/ame]

Great advice being given here and I also wanted to add, never trust pet store employees..they give sooo much incorrect advice it amazes me. It is complete rubbish that if a rat has another rat with it, it will not bond with humans as well. This is blatantly untrue.

A happy rat is one with at least one buddy to play with, feel safe with, cuddle, groom and a million other things that rats need from other rats, but it has nothing to do with the rat/rats bonding or not bonding with their people.

As one of my rat books said, "Even if you have twelve rats, they will ALL still want to come out and interact and be loved by their humans."