Most economical setup for 3 rooms; new customer

I am interested in getting some Sonos equipment, but not necessarily the most expensive. I would like speakers in 3 rooms, and think 1 speaker in each would be fine. The options are a bit overwhelming, so would like input from those who have experience. Ideally, I would like to play one channel (from Calm) on all 3 simultaneously.

I might start with 2 rooms, and then add one later, depending upon the cost.

Thanks.
Ruth McClain