A new rabbit

Question
My friend has a small rabbit that is very sweet and loveable. She is tried of taking care of it and wants to get rid of it. My sister and I really want to bring it to our house but there are a few problems. We have a bunny of our own and we don't know if they'd get along with each other. We also don't know either of the rabbit's genders, and we wouldn't really want them breeding. I was wondering if you have any input or suggestions as to what I might do and if any situations could be altered in order to allow our bunnies to live together. Thanks for your time!

Answer
As to the gender, if it's at least 4 months old, boys are pretty easy to spot.  But just in case, this page has some picture to help sexing rabbits.  Go to the bottom of the page and there are links for boy and girl:
http://www.rabbitnetwork.org/articles/sexing.shtml

Next, rabbits even if they are the same sex, have an easier time getting along if they are all fixed.  Usually, you don't have as intense territorial behavior if everyone has been fixed.

If you do bring the bunny home.  You have a better chance if you take your time with face to face introductions.  And keep in mind, not all bunnies will get along.  That doesn't mean they each can't have a lot of exercise and people time, but just not together.

Try to keep the rabbits in separate cages or parts of the house for awhile.  You can switch cage items and let each rabbit get used to the scent of the other.  Also, one rabbit can be out exercising while the other is in it's cage.  This is a good way to get a sense of how the rabbits may interact face to face.  Hopefully, disinterest or curiosity is what you will get.  If there is any hint of aggression, you'll have to go slow.

When you do decide for them to meet face to face, do it in a neutral area like a room they've never been in or the bathtub.  Have a squirt bottle or towel handy in case they fight.  It is likely that one rabbit will mount the other, even if they are the same sex.  Mounting is also a dominance behavior.  If the ears go back and the tail goes up, a fight may break out.  You want to try to intervene before it happens.  

These sites give good tips on bonding:
http://www.rabbit.org/faq/sections/introductions.html
http://www.rabbit.org/journal/4-4/tough-bonding.html
http://www.rabbitnetwork.org/articles/bond.shtml

This may be overkill.  Who knows.  Occasionally some rabbits hit it off after a short time.  Others not so much.

Good luck