I think you are confused about what the IRS considers a business or not.
The IRS has written on this issue regarding
a person who makes investments for a living with Topic No. 429 Traders in Securities (Information for Form 1040 Filers) which classifies individuals as: Investors, Traders, and Dealers. Skipping Dealers as they have obvious customers,
So an Investor:
Investors typically buy and sell securities and expect income from dividends, interest, or capital appreciation. They buy and sell these securities and hold them for personal investment; they're not conducting a trade or business. Most investors are individuals and hold these securities for a substantial period of time. Sales of these securities result in capital gains and losses ...
Or a Trader:
Special rules apply if you're a trader in securities, in the business of buying and selling securities for your own account. The law considers this to be a business, even though a trader doesn't maintain an inventory and doesn't have customers. To be engaged in business as a trader in securities, you must meet all of the following conditions:
- You must seek to profit from daily market movements in the prices of securities and not from dividends, interest, or capital appreciation;
- Your activity must be substantial; and
- You must carry on the activity with continuity and regularity.
The following facts and circumstances should be considered in determining if your activity is a securities trading business:
- Typical holding periods for securities bought and sold;
- The frequency and dollar amount of your trades during the year;
- The extent to which you pursue the activity to produce income for a livelihood; and
- The amount of time you devote to the activity.
If the nature of your trading activities doesn't qualify as a business, you're considered an investor and not a trader. It doesn't matter whether you call yourself a trader or a day trader, you're an investor. A taxpayer may be a trader in some securities and may hold other securities for investment.
So returning to your smartphone example, that $4000 in devices would be considered an Investor (research) expense, as you are buying the stocks for growth and income and not for daily movement.
Additionally as an Investor staring for the 2018 tax year you are no longer able to take the 2% Misc. Itemized Deduction, see IRS Pub 529 Miscellaneous Deductions. Note that even in prior tax years, the smartphone purchases would probably not have qualified as an investment management expense.
So the answer to your question:
So $32,000 trip costs is tax-deductible, but the $4,000 research costs is not?
is YES or at least the business part of the $32,000 trip is tax-deductible. As others mentioned, a YouTuber is either a self-employed entertainer or works for his/her entertainment company. The Google company, YouTube, submits a 1099 to the IRS for payments made to the entertainer (sole proprietor/corporate). That entertainer would need to declare all income like brand sponsorships, pay assorted payroll taxes, business expenses, etc and do so at sole proprietor / corporate tax rates. By being a business the entertainer is allowed to deduct business expenses.
The IRS doesn't consider an Investor a business. Investors' already have a lower capital gains tax rate compared with regular income and isn't subject to payroll taxes on those realized capital gain earnings.
And you sort of asked about real estate in the comments, the IRS has written about Rental Income as well in Topic No. 414 Rental Income and Expenses. So while you won't be paying payroll tax on the earned rental income there are still a number of business-like behavior you'll have to follow, like depreciation.
So a YouTuber is closer to traditional business than either an Investor or earning Rental Income as both have specific rules from the IRS.
Follow up to comments
But what about buying one smartphone per two years for your buy and sell of stocks? Then it is tax deductible for a trader but not for an investor?
Traders report their business expenses on Form 1040, Schedule C, Profit and Loss from Business(Sole Proprietorship), yes a Trader would be able to deduct the portion of the smartphone cost used for business.
Then if you are into rental properties, then if you take a trip to Phoenix or Boston to see if you should buy a condo or house there as a rental property, then the costs of that trip are tax deductible?
Reminder, Individuals are not businesses. Individuals spend time researching lots of things which may or may not be of benefit: "visiting various houses before a purchase, comparing car prices, visits to private education facilities for children of special needs or religious beliefs, subscriptions for analysis of investment funds". All of this "research time or research resources" to my understanding is NOT deductible.
Once purchased/transacted certain items' on going cost do become deducible as per IRS rules. So to my understanding your "trip to Phoenix or Boston" would not be deducible as the property hasn't been purchased yet. However once bought, you can
deduct the ordinary and necessary expenses for managing, conserving and maintaining your rental property. from What Deductions Can I Take as an Owner of Rental Property?
If you think my interpretation is in error please cite as I have done IRS documentation which differs.