I have a female ferret, Sheeva, and I'm thinking of getting another one.  I plan on going back to work full time and I don't want her to be lonely.  I have a dog, Bailey, thats her buddy now but when I'm at work my mom will be babysitting the dog.  Sheeva isn't quite a year old yet and she's on the small side.  Should I wait until she's a year old or not? Also I know w/ dogs that males and females tend to get along better then same sex matches, is that true for ferrets?  And if I get a male I know breeding can be dangerous so how much is it to get a male neutered?

Your female isn't spayed? Just that by itself is dangerous since an intact female can die if she's left in heat for too long.

If you adopt a male from a shelter, he'll be neutered.

And you would be surprised at how well those small females can fend for themselves. My sister has 2 females who are on the very small side (one is 1.5 pounds during the winter and the other isn't much larger) and they love playing with my large boys who weigh around 4 pounds each during the winter.

I don't know if she is spayed or not.  I can't see a scar on her belly but I really don't know what to look for.  I got her from a pet store when she was a young kit (wasn't sure on her age either but she's doubled in size).  How much is it generally to get a ferret spayed?  Also is there anything to stop her from being in heat too long and how do I know if she's gone into heat?

If you got her from a store, she's spayed.

Your female is spayed.
 
The pet stores spay and neuter their ferrets, so if you buy a male from a pet store or shelter, he will already be neutered. :)
 
 

I have 2 rather small females (1.5 lbs each)  and 3 males (2.5 to 3.5 lbs each) each came at different times, I do watch my largest boy, Potter, with Justice, she had a back injury and doesn't get around as good and  he is just rough. The little girls do get in there and romp n roll with the boys.  Miss Fang uses the sneak attack, she will hide in a tube for her attacks, Justice does the same but from under their blankies.