That seemingly simple idea is actually a radical departure from conventional practice, and requires some financial and regulatory gymnastics. Under current law, only wealthy “accredited” investors (typically those with a net worth of $1 million or more) are allowed to invest in private firms.

But recent changes to securities laws ushered in by the Jumpstart Our Business Startups Act, signed into law in April 2012, will soon make it much easier for the Millers and other new-breed developers to “crowdfund” real estate.

Under that law, unaccredited investors may invest up to $2,000 a year, or 5 percent of their income or net worth (whichever is greater), in private firms, like a real estate limited liability company, as long as the investment takes place on a site or broker-dealer registered with the Securities and Exchange Commission. The law, however, has been bogged down at the S.E.C., which missed an end-of-year deadline to complete rules.

Until then, crowdfunding companies must either restrict investments to accredited investors or, as Fundrise has done, register each development project with the S.E.C. — a process that can take months and tens of thousands of dollars. For now, says Benjamin Miller, offerings are being subsidized to prove the concept. But the brothers hope that eventually the process of offering shares to the public will become much easier.