Most profitable ideas are something that solves a problem you or one of your founders and who's customers would be businesses or individuals who could save/make money using your service in their own business.
Listen to the archive starting at episode 1 Rob goes from drop shipping beach towels and jobs websites through a couple successful software products to founding and exiting with Drip.
http://www.startupsfortherestofus.com/archives
For Inspiration Checkout the businesses on indiehackers. Listen to their podcast too. https://www.indiehackers.com/products
Good Advice - DHH Startup School https://www.youtube.com/watch?v=0CDXJ6bMkMY
Listen to the archive starting at episode 1 Rob goes from drop shipping beach towels and jobs websites through a couple successful software products to founding and exiting with Drip. http://www.startupsfortherestofus.com/archives
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