Maybe existing DHH style companies are a good area to look for inspiration to build free alternatives with some premiums added afterwards... Like flickr added pro accounts for $25/year. Read Wired's "Why $0 is the future" http://www.wired.com/techbiz/it/magazine/16-03/ff_free

Building less of an app also means it will be easier for others to come later and build what you made and give it away. Look at how it took 2 people at Google a few days to build HuddleChat which some said was too similar to 37signals' campfire.