Tandem double stroller

I have an 18 month old and with another on the way, I want to get a double stroller. The ones I want are so much though. I don't like the side by side seats because it's too wide to easily get through crowds and I live in Los Angeles. I really like the Phil and Teds or the Baby Jogger City Select with a second seat. They look sleek, compact and can be used as a single by removing second seat. They cost $500+ though! Does anyone have experience with these or have another recommendation? I could probably find one of these in good used condition since I live in such a populated area. I can't afford this brand new.