The true test is when you initial sphere runs out where do you generate business and HOW?

The IRS uses a test of 20 factors in the determination. 

Doctors used home office to treat emergency patient failed the regular test in the tax court. it will not qualify for the home office deduction if use is only occasional.Exclusive-have to be exclusive, and has no other use of the space. 

test the market, do a property or two and if you like how it goes you can always grow from there. 

Thanks Scott, I did run some craiglist test ads and got 4-5 response within a week or two.

I think a more effective way would be to have some sort of education class/test that you could pass to bypass the rules and get some sort of certification that would allow you to invest. 

So I went back and did a program that was a mix of being able test out of courses (with full credit) and online.

I call this my "roach test": if I see one, there are probably 100 others I can't see and move on to a house that at least looks to be roach free.

I am considering building one or two and AirBnB them just to test the market. 

But investors should start stress testing their properties and income streams and prepare.