“NEVER work for free” is a well-intentioned – but slightly misguided – common piece of freelance advice.

I understand why it’s out there! It’s true that far too many freelancers undercharge for their work, and even more would-be freelancers end up as over-exploited volunteers.

But a better rule is to “RARELY work for free”: there are a few circumstances in which it is smart – and even laudable – to offer your services gratis.

1. When you (really) love it

If you’re working for yourself, or on a real passion project – feel free to work for, ah, free.

Sometimes money is just not the object; sometimes you need to invest your time in a project that doesn’t necessarily lead to riches, but that feeds your soul.

Don’t let the lack of obvious remuneration keep you from pursuing something you love. There are more rewards out there than can be counted in dollars and cents.

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2. For an (incredibly) good cause

One of the nicest things about freelancing is the opportunity to use those skills to give back to your community. Now, DON’T use this as an excuse to regularly work for free.

Plenty of non-profit organizations can afford to pay freelancers, although you may choose to offer a discounted rate (I generally charged NGOs a bit less than corporate clients, because that just feels right – but that’s just personal preference).

But if you want to volunteer – particularly if you really believe in a cause, or if you’ve got extra time and much-needed skills – there is no more laudable sentiment.

It feels GOOD to use your skills FOR good… and there’s nothing wrong with doing that for free.

3. If it (absolutely) fills a gaping hole in your skills

This is the trickiest exception to the rule. Proceed with caution.

If you find yourself on your fifth “pay by exposure” job in a row, you’re being had – start charging! You deserve to be paid fairly!

But if an unpaid gig will REALLY build a skill that will take you to the next level – if, for instance, you’re just starting out and an internship will teach you how to program/run a specific business/work in a specific trade, or build your resume in a very significant way – it may be worth thinking of it as a class.

The upside is you don’t have to pay for your “class”; the downside is that you’re working for free.

The key is to do the unpaid gig for a FINITE time; otherwise, you’re a volunteer.

Even if most of these elements are true – even if it’s a passion project, for the public good – you may someday want to start making a living doing it.

Don’t be afraid to start asking for fair compensation when the time is right; doing so is what makes you a professional.

RARELY work for free – don’t be a full-time “free”lancer, and the occasions on which you do work gratis will become joyful exceptions, that you do without resentment or hesitation… because they are within YOUR control.

Kate Hamill lives and works in New York City, where she consumes an inordinate amount of Sriracha daily. You can catch up with her on Twitter at @katerone.