Glad to know none of us is alone when dealing with a loving, but sometimes hard headed, spouse. My husband had no idea what was about to hit him when we got married. He knew I wanted dogs and wanted to show them, we started at one, now we have four, and next year will add another of our own breeding. He has lovingly put up with it, even if he grumbles about it sometimes. Because we don't have small dogs, we have large 90lb dogs. Everything is bigger and more expensive. But he loves the dogs now.
One day I decided I wanted chickens. I went out and brought them home. Had them set up and cozy before he walked in the door. He was really not all that happy about it. But, he loves me(Still, can you believe it?) and he loves welding, so he made me a beautiful coop. Which I told him he could build and sell others like it for a profit. He found that idea intriguing. Now, he adores the chickens and is Very proud of them. He told all his co-workers about the eggs we started gathering and showed his friends our egg carton when they visited. He collects bugs for them and feeds them bites off his apple or whatever he is eating. I tell him we are going to get more and he says 'ummm, I don't know about that!' - but I know he won't mind. He is fascinated by them and it has proved to be a great experience for my entire family. My parents too love being around the chickens. Even my mom who was afraid of them(a rooster attacked her when she was a young child) is happily sitting outside with them during the late afternoon. So, yes, adding another living being to the household does take work and time and effort. But once you start collecting those eggs and see what joy it brings, it seems to soften the edges of everyone around and it is a happy peaceful feeling. My husband loves to hear the chickens cluck and talk. I am sure your husband will too.
Perhaps if you help him see this isn't just a passing fad, and that you have done your research and have a plan of action. Let him know the pros of keeping chickens(chicken poop is great fertilizer, eggs, they eat insects etc,) and also the cons(I can't think of any off hand, but there might be some). Give a detailed plan of how you will overcome and deal with the cons. Also share how you would really love doing this together, and if it just isn't working out you will re-home them. Sometimes if they know they are not locked into a deal it makes it easier.
Sorry for my rambling, I am fighting a cold and on pretty good cold medicine. So I tend to keep talking. Best of success to you!!!
I'll keep my fingers crossed.