I'd suggest adding contact info to your profile and talking about your problems here. Hopefully you'll pique some interest and have some email waiting later.
Since ideas are a dime a dozen: Glassdoor for Apartment Rentals: Tenants give their address and rent amount per month in exchange for access to everyone else's data. Know what other people are actually renting for, not landlord asking rates. Why is there no data on what your neighbor just signed his lease for?
Angelist for Real Estate
Imgur for Excel
Nextdoor for Office Buildings
I got loads more...got to be something worth making in there... :)
Also, city tech events might be a good place.. such as startup drink and the like. Just going there and listening to ideas.. but being on the looking for opportunities. I.e. Someone is telling how his startup isn't doing that well and might be on the lockout for a new venture.
Imgur for excel doesn't mean that much to me.. What's the context, the problem, the value proposition, the channels, etc.
Would love to hear more about your other ideas and tell you about the data and insights product I'm working on for property managers and others in the rental real estate space. Email is in my profile.
If any of your ideas would be potentially useful internally too, you might be better off hiring people rather than finding a cofounder.
Otherwise, following his description literally, he wants a web-based way to share read-only copies of random spreadsheets.
I am constantly searching for datasets from Government websites, market data, etc. Wolfram alpha has the data but its not free. The federal government data is bloated and takes forever to parse. Why couldn't someone post an excel sheet of the data for everyone to use?
This is a tricky game-theory scenario. It may work if all the tenants find the value in it. It may also implode for tenants or the land-owner.
"Why is there no data on what your neighbor just signed his lease for?"
If the info isn't public, most people that value privacy will not want to share this.
I'm not too sure about the other ideas, but maybe you need to think of something simpler, that helps address a problem that all people like you face.
Maybe the best idea in this case would be the simplest.