You could view a sponsor's history and look at the returns shown on their track record, but without context it's meaningless. 

Approached the seller asking they pay all closing costs, received enough credits to buy down the interest rate back into the 5-range (current rates were in the 7-range).

Cash flowing well on every SFH and small multi family deal I've done in Upstate NY, even with my first having an interest rate above 10% due to what my credit was.

Double taxation would be when you have to pay US income tax and then also Canada income tax and you don't receive a credit for your US income taxes.

Generally, the properties that benefit the most from a cost segregation study are properties that are remodeled, expanded, purchased or constructed after 1987, the year in which the Investment Tax Credit was enacted.

I will also be tracking expenses related to repairs, maintenance, travel to and from NV, hotel stays, meals, gas, and other regular business costs.In the long term, I aim to purchase additional properties under the business name, but I understand I need to establish at least two years of income and credit history before doing so.The issue I’m encountering is that my accountant has not provided any guidance on how to structure this scenario.

I usually work with my local credit union where I have developed a relationship over the years.

As mentioned seller credits are the best path as title insurance and taxes are pretty much fixed.

and how well my credit score will be?

It's a rare time in history for this.