One way or another, you will want to sell within 3 years after moving out so you do not lose the tax free gain on sale (up to 250k tax free gains for single and 500k for married).

Is sales tax registration required?

You should do something like this in cooperation with your accountant because you don't want to mess up your taxes and have to pay for something you shouldn't be paying for. 

The current rental income is $5,300/month, while our mortgage is $1,500/month, property tax is $600/month, property management costs $200/month, and maintenance expenses are currently unknown.We’ve utilized a HELOC from this property, amounting to $300,000, for renovating the basement and investing in a preconstruction condo and another property in a different city.

LLCS are sometimes important to the states who won't let you homestead (get a tax break) a property in an LLC. 

Worst case scenario is they take 8% of your rent money and then at the end of the year you get to take that as a deduction on your taxes.

A couple of my favorites are Opportunity Zone Tax Credits and Low-Income Housing Tax Credit (LIHTC).

What does the tax ID indicate?

The experience was very poor and began with a lengthy application, asking for all sort of documents including tax returns, rental schedule, voided check, credit check etc, just to get a pre approval letter.

I have even had situations where I had to amend my taxes because the tax person screwed up.