Working for free is the one unified enemy in today's freelance gig economy. People like myself who have been consulting for a while know that this no-no goes back years, though today's saying has a better, meme-ready ring: "Work for exposure? People die of exposure."

Once you get into the entrepreneurial field, though, then the world becomes much more gray. For instance, people begin to barter - some of my earliest entrepreneurial endeavors was from me trading my skills with another founder. People begin trading work for equity - in a company that may never be worth anything. Unlike the traditional contractor/corporation agreement, the entrepreneurial world can become complicated really quickly.

There are 4 great guidelines to make sure your free endeavors are smart, calculated risks rather than blind actions:

1. Treat it like a paid gig: Your free work should be of similar, if not the same quality as your paid work. It's your reputation on the line - if the person you're working with gets asked by another person about the quality of your work, then he or she is going to be honest about it regardless of whether you were paid. In fact, I can guarantee that the person asking about you won't care whether you were paid or not either. It's still reflective of your standards.

It also means not treating the client differently because you are doing it for free. Late or missed deadlines, dismissive attitudes and other issues can soil you rep as quickly as a bad deliverable.

2. Give an invoice: Consultants like leadership strategist Bernadette Johnson actually give their free clients an invoice with the current market price of their work and the term "Gift In Kind". It may sound strange, but it serves two great purposes.

First, the client is reminded that you are, in fact, paid for the services you are providing, and it helps them value the time you are spending on them more. Second, after the current opportunity is done, the client has a clear idea of what it will cost to work with you next time. If you did a good job, then they will also respect why you cost as much as you do, too.

3. Bring up the free part once, then never bring it up again: There are few things worse than someone doing something for you and then bringing it up to you again... and again... and again. Your personal life is your own thing, but within business, you should always be leaning on other trusted people for advice, resources and time, just as others will on you. In entrepreneurship, helping others isn't a charity act, but a means of survival.

4. If you don't want to do it, then don't do it: Seriously. Saying No will save everyone both time and energy. Here are a few great ways to say it.