FORTUNE — Are you the divorce attorney everyone calls with their marital woes? The accountant who finds that the dinner conversation inevitably turns to whether or not your friend’s new iPad or trip to Bermuda is tax-deductible? Maybe you’re the techie whose friends and parents’ friends call repeatedly with questions about uploading photos to the cloud or sharing videos online.
It’s great to be an expert in your field, and it’s flattering to be asked for your opinion or advice, but sometimes people cross the limits of personal and work-life boundaries. Just because Jonas Salk gave away the polio vaccine for free and Craig Newmark refuses to charge for Craigslist, you don’t have to be a philanthropist too. As altruistic as you may be, you don’t have to provide unlimited counsel to friends and family around the clock. You should be helpful when you can, but you are entitled to put meaningful limits on the pro bono advice you dish out regularly.
When you find yourself in situations that push the envelope, determine the amount of “free” time/energy you’re willing to dedicate to a friend’s issue and then give of yourself graciously within that time allotment. Next, give your friend or family member options of how you might continue to be helpful after their initial free pass.
Friends help friends. When someone near and dear to you comes with a question, issue, or problem, be generous and share your talents or expertise freely. Agreeing to spend an hour setting up someone’s email, 30 minutes reviewing a resume, or an afternoon brainstorming business ideas is well within the bounds of friendly advice and familial give and take. Spending a week setting up a website, troubleshooting tech issues endlessly, or drafting, writing, and reviewing an application to law school is crossing the line.
Think about the amount of time or energy that fits into your schedule without undue personal sacrifice and the amount of time necessary to provide real value to the other person. As a career expert, I’m happy to give an hour of my time to prepare for a friend’s performance review, script out asking for a raise or talk through a difficult conversation with the boss. I won’t, however, coach you regularly or talk to your employees for free.
Just as a houseguest eventually overstays his welcome, so too do people overburden you by assuming you’ll continue your role as adviser, counselor, therapist, problem solver, or life coach, indefinitely. After sharing your initial thoughts or giving some meaningful advice for free, it’s entirely acceptable to change the dynamic.
If the advice you’re providing is directly related to your profession or your side hustle, then be upfront and acknowledge you’ll need to put together an agreement to make sure you’re compensated for your time and energy going forward. If the advice relates simply to a natural talent or hobby but not how you earn your keep, you’re still entitled to be compensated.
Once you’ve established your inability to provide bottomless advice for free, you can then soften the blow. State that you’re willing to stay involved on a more casual level for free and serve as a background adviser. This shows you to be generous and genuine in wanting to help while at the same time protecting your professional integrity. It also gives your friend a way to save face if they never had any intention of paying you in the first place.
Offering over-the-shoulder advice after the more formal “you-should-pay-me” route communicates that there’s a difference between pinging you occasionally with questions and taxing you regularly with real or meaningful work that you should be compensated for.
Lastly, go ahead and recommend others who might help your friend’s cause. This demonstrates that you’re not trying to profiteer here — you genuinely have your buddy’s best interest at heart. Perhaps working together formally is just too awkward or uncomfortable, perhaps you don’t have the time or capacity no matter the financial arrangement, or perhaps you’re really not the best person for the job. Whatever the case, you probably know someone who can help.
You owe it to yourself to not undermine the value of your time. While you’re happy to give and share advice when appropriate, you’re not in the business of being taken for a ride. Have enough self-respect and confidence to value your time and energy appropriately and help out when you can. But don’t feel forced to do Aunt Edna’s taxes year after year, write Johnny college essays, or give legal advice for free.
Jodi Glickman is the founder of communication training and leadership development firm Great on the Job. She is the author of Great on the Job: What to Say, How to Say It, The Secrets of Getting Ahead (St. Martin’s Press, May 2011).