I seriously doubt the person built those things by himself. If he did, then I bet there's no electricity or plumbing, and it would've just been better to buy actual trailers as he could have a fleet of them delivered in a few weeks rather than spend years of hard labour building them himself.

I would imagine that fund-raising would work regardless as long as you're showing that this is a charity thing.

Of course, I bet any sort of joined home would be illegal there as it stands. Zoning laws are the absolute worst in most western countries, making anything but an expensive and space wasting single family house illegal to build in most housing zones. It's the single biggest reason why housing prices are so out of control, and will likely crash taking 30% of the entire nation's retirement savings with it in the next decade or so (since most people who buy houses and bet everything on being able to sell it at a massive markup for when they retire).

The issue with your suggestion is that you're presuming that this guy can keep building more buildings, but he sold his company to be able to do this. It's a one-time deal, unless if he manages to start another company, raise it to a great value, then sell it off again. Even then, that's a decade venture at least. Planning as well doesn't take that long, it's the approval process that does. Planning can be over with in less than a month, and that's presuming he doesn't go for an existing plan.

There are always people on the verge of destitution, so either save a handful today, or save several times that many a year or two later. Low and mid-rise apartments are not only massively space efficient, but cost only a fraction to build compared to a hundred individual homes, as the single building shares many of the same components for all the units. Not only does it use less parts, but the amount of labour is only a fraction of so many houses.