Well, it really depends on how many dogs you can actually handle at one time. When I was younger my parents were known to have three maybe more dogs at one time. However, the older i got the more my family realized that caring for so many dogs could be a whole lot of work. So now we tend to only have two dogs at one time and no more then that. Both of our dogs remain primarily outside, although they do come in on occasion.
As for you problem with your husband. I think it would be a good idea for the two of you to talk this out. You already have four dogs would one more, and a small breed at that really make that much of a difference?