All the IRS cares is that the taxpayer is the same. 

(i) has not attained the age of 19 as of the close of the calendar year in which the taxable year of the taxpayer begins, or(ii) is a student who has not attained the age of 24 as of the close of such calendar year.Here, in black and white, the law specifies that the determination is made as of December 31st and applies to the entire year.

Being a real estate professional allows you to treat the income as non-passive, allowing higher high income tax payers to pay less in taxes.

What this stems from is that the IRS requires that a taxpayer trace interest expense to the nature of how the proceeds are used. 

Second, for you as a taxpayer you need to evaluate if your tax situation (e.g. property type, tax profile, material participation, etc.) will allow you to leverage additional losses generate from cost seg to optimize your taxes. 

I would tend to agree with the other CPAs typically.The 500-hour test is one of seven material participation tests used by the IRS to determine if a taxpayer is actively involved in a trade, business, or rental activity. 

Does your mortgage include your property tax payments?

In California and Florida there are two State run plans of last resort (Cal Fair and Citizens respectively) for the otherwise uninsurable; properties that private companies have already deemed too risky and are effectively subsidized by taxpayers.

Not sure if everyone here knows, but I represent taxpayers before the IRS.

The interest on the rental is an offset to rental income, and is by definition deducted from your taxes.A 4% interest rate on a primary is like a 4.88% after rate for a taxpayer in the 22% federal tax bracket, or higher if in a state with state income taxes.