What are the best passive income ideas without investment?

There are several passive income ideas that don't require any investment, such as:

Affiliate marketing: Promoting other people's products and earning a commission on each sale.
Ad revenue from a blog or YouTube channel: Creating content that attracts viewers or readers and earning money through ads.
Printondemand products: Designing and selling products like tshirts, mugs, and phone cases without having to keep inventory.
Online courses: Creating and selling courses on platforms like Udemy or Teachable.
Renting out a spare room or parking space: Using services like Airbnb or JustPark to make money from underutilized assets.
Peertopeer lending: Lending money to borrowers through platforms like LendingClub or Prosper and earning interest on the loans.
Investing in dividend stocks: Buying stocks that pay out regular dividends to shareholders.
Licensing intellectual property: Earning royalties from licensing your creative work, such as music or art.
Remember, even passive income streams require some effort and time investment upfront to set up and maintain.