Double or single stroller???

Isabel • Anything can happen
Hey guys, so I just wanted an opinion on wether or not to get a double or single stroller. Im due in Dec. with my 2nd child and my first will be turning 3 yrs old in Dec as well, but I'm thinking once she sees the baby in the stroller she may want to get on it as well? She has her own and we still use it. I'm sure there are some mothers out there that have already gone through this, what should I do, my husband says get the double but if we don't have to spend the "extra" cash then I would like to save ourselves that money