If you have 3 car seats in your car, how do you have them set up? Do you have a 3rd row SUV or minivan? Do you fit 3 across?

I drive a toyota rav 4 and I think trying to fit 3 car seats across would require buying new carseats and even then I don't know if it'll work or if it's worth it. On the other hand we don't have a car payment right now and I really don't want one, ha. DS1 will be 4 when our 3rd is born, but he's small, so he's going to be in a 5 point harness for awhile still. So we'll need to fit in 2 5-point harness carseats and an infant seat.