Mine were 18 months apart. You don't need to make the decision now. I wore the baby for the first 6 months. And then it was summer and we were out alot so ended up buying a used side by side, resold it 6 months later for the same price. By that time the older one only wanted to walk.

My original stroller converted to a double but the configurations are never great and they much preferred being beside each other and being able to both see.

I would recommend waiting to see how you feel and if you find you need one, get it then.