Yes, Qustodio comes with a free plan, which you’re downgraded to after the 3-day free trial expires. I think the free plan is pretty good — it provides access to screen time monitoring, time limits, restricted time periods, and web filtering (including the option to enforce safe search). However, the free plan limits you to daily and weekly activity reports and 1 device, and it doesn’t provide access to Qustodio’s customer support ticketing system.
Qustodio’s free plan could be enough for some people, but I’d mostly recommend using it to test the service. Then, if you’re happy with Qustodio, you should definitely upgrade to its paid plans — that way, you also get location tracking, app filtering, YouTube monitoring, support for 5 or unlimited devices (depending on which plan you choose), and more. Plus, Qustodio backs each purchase with a 30-day money-back guarantee.