I'm having the hardest time finding a back to back double stroller that comes with a car seat. And I…

I dont think they make tandem strollers with car seats, you may need to purchase separately. I have been researching double strollers, and all of the ones I have come across dont have any car seats included

Then how do you know for sure the car seat will fit the stroller so stressful. I found one with the car seat but it was like 600 dollars

Im buying the contours options elite, and using the britax car seat that I used with my first baby. I bought a gender neutral car seat cuz I knew we would have another baby within 2 years of the first

Most tandem strollers dont have an insert for the carseat, they need adapters. You will most likely need to purchase an adapter. Check the description area of the stroller, and google car seat adapter for "insert double stroller name" The adapter for the contours is about $20 with walmart online

Okay Thank you @rachel8792