Chimney Caps

In a new house that I am about to purchase, there is a masonry fireplace in the living room, with a brick chimney that is two stories high on the side of the house. There are two flues within the chimney, one for the fireplace and one for the boiler & hot water tank. I have the following questions regarding chimney caps:
1. Is one necessary?
2. What is the purpose of having one, besides keeping out birds, rain, etc.? Any benefits to a better burning fire?
3. Are there certain ones that are better than others?
4. Can you recommend any particular ones and where on the web can they be purchased?

Any comments appreciated. Thanks

 

1. Yes, better to have one.
2. No, a chimney cap isn't necessary, unless you want rain, ice and snow coming down the chimney.
3. I personally like the rotating cap type that rotate and face away from the wind and draw the flue fumes and smoke out.
4 Just go to your local big box store or building supply, and get what you need.
This is not an expensive decision.
Your call.
Good Luck!
Mike