Summary: For those with a W-2 job but that own 1 or 2 rental properties, are there any expenses that you declare that aren't to one specific property, but are meant to support / grow your real estate investing in general?

A bit more of an explanation...

I've been reading a bit about taxes lately ("The Book on Tax Strategies" by Amanda Han and Matthew MacFarland was a surprisingly interesting read), but one part that I'm a bit confused on is when one can begin to take advantage of the non-obvious deductions for rental properties. 

I have a W-2 job but am currently closing on my first property in the next month and plan to add 1 or 2 more to my portfolio by the end of this year. All properties will be out-of-state. 

Besides the standard deductions like depreciation and mortgage interest, there are other more business-like expenses that contribute to the growth of one's real estate portfolio. Some examples:

• Using a home office for communications with my property manager, agent, etc.
• Attending a real estate conference or training

I've been reading on various forums that REI at this level (just owning a few properties on the side but having a W-2 job) is considered an investment and not a business, so the types of deductions mentioned above wouldn't apply. But others seem to say the opposite.

Does anyone who owns a few properties (not in any business entity) while having a W-2 job take advantage of deductions like the ones mentioned above?