IIRC, I was looking up the prices of various lots, and many homes were $1000! Now, I don't live anywhere close to Detroit, but the idea of spending maybe $10,000 to $100,000 for dozens or even hundreds of houses is interesting.
Developing for humans may be a problem: Hundreds-of-thousands of people have left Detroit, leaving the city in the state that it is in today. But the houses and infrastructure (roads, water, electricity) may be useful for some niches, even in a "ghost town" situation (Or perhaps: more of a "ghost suburb" situation. Neighborhoods with shrinking populations will naturally have weaker schools, causing more people to leave, causing taxes to go up on the remaining people, causing more people to leave, etc. etc. Its a bad death-spiral effect).
I think I recall an article about how one writers group was buying up neighborhoods to station writers-circles, effectively creating a community of writers imported from around the country to one location, so that the writer-circle can leverage each other as an author support group.
I haven't heard of this Bee Farm thing, but I would have expected that sort of thing to be better in a more rural community.
In any case: redeveloping all of that land and making it useful (as opposed to broken down neighborhoods with crumbling infrastructure) is a big question for Detroit... and investors / businessmen. There's probably a lot of opportunity there.