I never borrowed against my crypto to expand my stake, but I can and do leverage my property investments.Getting taxed on the sale of your crypto hurts.

If you have an entity with an EIN, and that entity either owns the property (named on title) or constructively owns the rental, then use that.Otherwise, then SSN.Ultimately this has very little effect on the tax return, liability, etc.

Only interested in STR due to tax benefits unfortunately. 

To improve your credit, you can start by paying off any debts you owe, keeping an eye on how much of your available credit you use, and fixing any mistakes on your credit report.

Looking for advice on how to maximize tax benefits on an upcoming conversion of my primary home to a long term rental (temporarily).

Everything has gone up in the last few years around this home.2nd house is $900 (property taxes increase yearly) now.

Are there any tax implications or mortgage barriers to building a home under the "second home" plan and then converting it to an investment property shortly after its finished?

You get some negligibly protections in an LLC too, and possibly tax.

Underwrite allowances for - Vacancy, Prop Taxes, Insurance, Utilities, Repairs & Maintenance, a Reserve Account, and Property Management. 

You'll want to make sure you understand the K1/tax filing implications because if you own very small piece of let's say 10 properties in 10 different states you would potentially receive 10 K1s (one for each deal) and 'may' have tax filing requirements in 10 states.