On Word Hippo all the antonyms mean "expensive".
But I need one word as the opposite of "for free" at all regardless of the amount.
That is "on paid basis" but something more shortly
For example in the sentence, "Try it for free. Then continue on paid basis"
An adverb would be the best.
Just found the following text in A guide to paid subscriptions:
When trying to decide whether to go paid, start by taking...
So, can we use "paid" as an adverb?
Ok, I've got the point regarding "go paid", I see I can simply specify fixed price after saying about free feature (but it's not my case) and the second part is redundant in my example sentence where it's implied that the next features are paid.
Still, I would like to find the general opposite of "for free" answering to the question "how" (how to go: for free or ?) more broadly regardless of the context. "How to go" and not "what feature": free or paid. That is not an adjective.
I've also found "go for paid". For example, going for paid is the opposite of going with organic (free) advertising of website here: Paid vs Organic; Digital Marketing's big debate
Is it correct to say "... Then you may continue the next stages for paid or stop our cooperation ..." ?