Bitrix24 Cloud is free, and not just for 30 days! However, when you decide to try out paid features and tools available in Bitrix24, you can activate your 30-day demo version (log in to your Bitrix24 Account, then go to Subscription > Activate Trial. When the 30-day demo period expires, you can either switch to one of the commercial subscription plans (Plus $39/mo, Standard $99/mo or Professional $199/mo) or continue using your Bitrix24 account with a free unlimited users for communication tools & 12 users limit for business tools.
Bitrix24 On premise (self-hosted version) is also available as a free 30-day trial version for installing the product locally or on a remote web server. If you choose to go commercial during the 30-day evaluation period, you can simply purchase a license key and use it to switch your trial product copy to a commercial one. No data will be lost, no time will be wasted for installing the product anew! You can download your Bitrix24 on premise (self-hosted) trial version here.