Nests and breeding

Question
I recently acquired three society finches from my boss.  I have read through several websites about finches yet I am certainly a newbie.  I would like to get them a nest to sleep in, but I don't want breeding.  Is it inevitable that if a nest is in the cage, the birds will breed?

Also, my boss would like to give me a fourth society finch when it regains it's health.  Is it safe to simply put the new bird in the cage with the others or will they fight?

What are the basic essentials for society finches?  I have cuttle bone, a bird bath, food, water, cage cover, and perches.  Is there anything else that I should get?

Thanks.

Answer
They may but not always. Even if they do you an take their eggs away, stick the eggs in the fridge overnight and then give them back. Let them sit on the duds for a couple weeks and then take them away. So yes, VERY good idea give them a nest.

It depends on the sex of the other finches. If it's all females or mostly females then yes. If it's mostly males (and unless this finch will even out the numbers) then no. Males will attack and possibly kill each other for the females. If this makes everything even then go ahead and stick them all together.
On a side note, even if the birds are healthy I recommend to take them to a qualified avian vet to get them checked over. Also, check for sac mites (this can be done by holding them up to your ear and listen for clicking). If you hear clicking then it is best to order something called Scatt from a website called www.ladygouldianfinch.com. They have everything under sun there that your birds could possibly need. Since I see that you are in the states, this will be cheaper for you since the website is in the states as well.

The perches need to be a varying width so the birds don't get arthritis in their feet. Also, make sure that the food is enriched with all sorts of nutrients. The food should come from a reputable pet store such as PJ's pets or Petsmart (don't know if you have those there but these are big retail chains in canada). Don't go buy bird food from bulk bins or some dirty store that stores it in a barrel or something like that.
Long story short, make sure you are getting their supplies from a place you would buy your own (I don't know about you but if I'm buying food for myself I want it from a nice clean store over some stall on the side of a highway).

I hope I have answered everything. If I haven't, please tell me and I will do my best to answer them