Running it
Pricing, scope and saying no
The transferable part is not the subject matter; it is running a one-person service business.
Guides on Running it: The admin that turns income into a trade
Nothing about the subject matter of this work transfers anywhere. Everything about the structure of it does, because the structure is a one-person service business with real money in it and unusually fast feedback.
Most people who run a service business learn these things over years, badly, on invoices large enough that each mistake is expensive.
Pricing, under conditions where you find out
You set a number, publish it, and observe what happens within weeks. That loop is rare, and it is the condition for learning: Kahneman and Klein's 2009 review in American Psychologist concluded that trustworthy intuitive judgement depends on a predictable environment and the "opportunity to learn" its regularities.
What it teaches, specifically: that price is read as information about quality in any market where quality cannot be verified in advance; that the bottom of a band selects for the buyers who cost most to serve; that a discount on identical work retires the card it was discounted from; and that raising a price is a different operation from setting one, with different evidence behind it.
The mechanics are in the pricing pillar, and they are portable more or less word for word.
Scope, and the sentence that defends it
The single most useful habit this trade installs is writing down what a job is before starting it.
Two sentences, before work begins: what will be delivered, by when. That confirmation is the whole defence in the one job out of fifty that goes wrong, and the reflex of producing it survives into every freelance arrangement, contract and favour you are ever asked for.
The second half of the same skill is pricing an addition rather than refusing it. "That is a separate job, here is what it costs, happy to start now" is a sentence that buyers accept far more readily than earners expect, and learning that people do not resent being charged is worth more than any single technique in the trade.
Refusal, without an essay attached
Saying no quickly and without justification is a learned skill, and this work forces it early because the alternative is immediately expensive.
A job you should not have taken costs a review, and the review outlives the fee by a year. So you learn to decline in one sentence, without an explanation - because an explanation invites negotiation - and to do it fast, because a slow no is worse for both parties than a quick one.
The buyer-side literature on how a commission is expected to open and close, including how a decline reads from the other end, is Rate Penis's subject rather than this site's, and it is a short and clarifying read.
The unglamorous half
Records, separated money, a tax reserve taken at the point of payment rather than at a deadline, and a monthly hour spent on your own numbers.
That habit is the difference between income and a trade, and once installed it does not uninstall. Running this as a business is the full operating picture, and none of it is advice for your jurisdiction, which is itself part of what you learn: that the answer to a tax question is always country-specific and never a forum post.
What does not transfer
The domain knowledge, obviously. The measurement conventions belong to a site that documents them properly, and the scoring internals to the technical account of automated assessment; neither will ever be useful to you again.
Your reviews do not transfer either, because they belong to the platform hosting them. Nor does ranking, nor a listing, nor anything else that looked like an asset while you were inside it. The platform-specific parts of your setup are exactly that - Rate Cock's judges page documents its own and no other.
What leaves with you is a person who prices deliberately, scopes in writing, declines quickly and keeps records. That is a smaller list than the inspirational version would offer and a considerably more useful one.