Good suggestions. I have many of these. One word about the “app” idea. I had a great idea related to personal taxes that I tried to get off the ground with my accountant as a partner. I would say it’s difficult to do this unless you have a coder on your team. Hiring someone is not really viable financially unless the app is simple. When we finally got the quote for a coder to write what we wanted (and after doing lots of mock ups ourselves and getting a demo for investors) the estimate was about 750k just to really get started.
While reading a very interesting book recently about the conquest of the Northwestern Territory (it’s Ohio, not Oregon for those of you who aren’t history buffs) I realized that the founding fathers of the US were all unabashed capitalists. Washington, Hamilton etc all held title to huge tracts of land West of the Appalachians that they had been speculating in for decades. Forming the US Army (a standing army was a big deal to a people who at the time equated a standing army with tyranny) and conquering the Iroquois was, in at least some respects, about profiting on their investments. While WCI readers probably don’t have any plans to conquer other nations, the real point of all this financial stuff we talk about on this blog is to turn yourself into a capitalist as quickly as possible. While capitalism has its issues, it’s still the best economic system we’ve found yet.
I prefer assets that make me a high return for the lowest amount of work possible (semi-passive involvement). And assets that pay me in several unique ways. Cash flow is only one way RE makes money for me. I also get principal reductions, appreciation, tax advantages (depreciation), and I control the rental increases on a yearly basis. Plus a majority of the capital is provided by the secondary market on 30 year fixed low interest rate debt.
For a closely held corporation, the passive activity loss is the excess of passive activity deductions over the sum of passive activity gross income and net active income. For details on net active income, see the Instructions for Form 8810. For the definition of passive activity gross income, see Passive Activity Income , later. For the definition of passive activity deductions, see Passive Activity Deductions , later.
The E-Commerce model is an interesting one. The idea is that you get products made cheaply (usually China) through a site like Alibaba, ship them to a warehouse (or your own house!), put the product description up on Amazon (or your own website), get some sales and then send out the product. There is a big learning curve with this one and you need some money up-front to get the products.
If an investor puts $500,000 into a candy store with the agreement that the owners would pay the investor a percentage of earnings, that would be considered passive income as long as the investor does not participate in the operation of the business in any meaningful way other than placing the investment. The IRS states, however, that if the investor did help manage the company with the owners, the investor's income could be seen as active since the investor provided "material participation." 
One of his favorite tools is Personal Capital, which enables him to manage his finances in just 15-minutes each month. If you sign up and link up an investment account with $1,000+ within 40 days, you get a $20 Amazon gift card. They also offer financial planning, such as a Retirement Planning Tool that can tell you if you're on track to retire when you want. It's free.

Another way to obtain real estate exposure in your portfolio is through the purchase of Real Estate Investment Trusts or REITs.  A REIT is a company that owns or finances income- producing real estate.  REITs are usually structured as a mutual fund so you can purchase REITs on major stock exchanges and offer several benefits such as real estate exposure, diversification, low correlation with financial assets, and potentially higher income than regular equities.
That said, from time to time I enjoy writing about some of the “other roads to Dublin.” Fancy investments are interesting and sometimes have different risks and rewards when compared with a basic index fund portfolio. Entrepreneurship has changed my life and that of many other physicians. Early financial independence opens all kinds of other doorways in your life. So in a blog about all things financial for high earners, from time to time I write about these other subjects. Today is one of those days.
**The information contained herein neither constitutes an offer for nor a solicitation of interest in any securities offering; however, if an indication of interest is provided, it may be withdrawn or revoked, without obligation or commitment of any kind prior to being accepted following the qualification or effectiveness of the applicable offering document, and any offer, solicitation or sale of any securities will be made only by means of an offering circular, private placement memorandum, or prospectus. No money or other consideration is hereby being solicited, and will not be accepted without such potential investor having been provided the applicable offering document. Joining the Fundrise Platform neither constitutes an indication of interest in any offering nor involves any obligation or commitment of any kind.