Also be careful with the verified funding providers they refer to.  

The majority of taxpayers are required to settle their tax dues by April 18 to avoid penalties and interest accruing on any outstanding amounts after this date.For those residing in Maine and Massachusetts, the deadline is extended to April 19 due to the Patriots' Day holiday in these states.How to Request an ExtensionIf you find yourself in need of an extension, the IRS provides convenient options to make the process smoother:File Form 4868:Utilize your tax professional, tax software, or the IRS Free File platform on IRS.gov to submit Form 4868.Individual taxpayers, regardless of income, can leverage Free File for an automatic extension request.Electronic Payment Method:Make an electronic payment using Direct Pay, Electronic Federal Tax Payment System, or debit/credit card or digital wallet.When selecting the payment type, indicate it's for an extension.

I have only owned one investment property (residence turned rental) which I sold at a great time, and now looking to get back into long-term SFH or multifamily investing more seriously to diversify my investments (I'm almost entirely in equities now). 

No need to test just be careful with it (don't eat, wear respirators, clean up thoroughly, have drop cloths/paper down, and disclose it to buyers). 

I cannot write off interest payments because I already have $10000 (cap) in interest that I am writing off as part of my primary residence.  

Lower-income residents bear the brunt, with vacancies for apartments under $1,100 dropping below 0.4%.

If you leave the property in your own name anything in your name is at risk, including your personal residence, savings, and future income.

The creditor could object if they are not taken care of in the plan according to their filed proof of claim (They filed an accounting with the court stating what is owed).

I personally do not like the idea of taking a loan against my primary residence to buy investment properties.

In CA virtually everyone who has lost money in CA RE did so because they were forced to sell usually due to being over extended.