I’m a 45 year old business owner who also has focussed on diversifying my income streams. I have a short term vacation rental in Florida that I bought for $390k in 2012 and net rental income for the last three years has been growing steadily. 2015 I am at $70k gross right now but should end up at $80-85k with net around $45k plus we use the place about 35 nights a year.
Further playing off of your talents and ideas, you can easily sell products online nowadays, too. Find companies where you can sell your musical talents for jingles. Look for companies who need freelance designers. While you can earn passive income through these royalties, again, it will take time and work to produce your craft, whatever it may be.
If you can save a lot early on in life, you can build up sources of unearned income, and this income will be exempt from payroll taxes. This is good news for investors and for retirees. Any pre-tax salary deferral contribution made to a retirement account, pension plan, or other pre-tax contribution will lower the amount of federal and state income tax liabilities, however, they do not lower your payroll/FICA tax - the FICA tax has already been taken out of gross wages. 
I am an English major and a herbalist with so many ideas and no extra income to fulfill them. I recently started renting my extra apartment in the attic with Airbnb. It’s amazing how fast I accumulated some money for few hours of work between guests. Now I want to persue all my dreams of opening an online herbal store, publishing my ebook of treating Ulcerative Colitis with herbs, blogs, and videos, and pretty much all of the ideas mentioned here. I will save this article as its really helpful for whomever needs some ideas…