There are three options for speaker rental currently available, as found by The Verge: "For Every Room," which offers two Sonos One speakers for €15 ($16) per month, the "For Your TV" package which includes a Sonos Beam soundbar in addition to two Sonos One speakers for €25 ($27) per month and the "For Home Theater" package which includes a Sonos Playbar, a subwoofer and two Sonos One speakers, plus free installation if you live in Amsterdam, for €50 ($55) per month.
For comparison, in the Netherlands a Sonos One costs €229 ($251) to buy, a Beam costs €449 ($493), a Playbar costs €799 ($877) and a subwoofer costs €799 ($877). Sonos says the subscription is flexible and can be adjusted or cancelled every month. So for home cinema fans who are renters or who want to try out the products before putting a lot of money down, the service could be a good option.
A Sonos spokesperson confirmed that Flex is limited to the Netherlands for now and that the company doesn't have anything to share regarding its expansion plans.