I'm going to reiterate what's already been mentioned above, but I'm going to actually give you examples of why it's relevant to you to find a U.S. tax professional.1 - You're going to need to file U.S. taxes once you have property down here, there's federal filings, state filings, and sometimes local filings too2 - Tons of tax treaties between the U.S. and Canada that are easy to miss and can cost you a lot of money (important one with rentals - effectively connected income - if the professional you talk to doesn't know what this is, run away)3 - The amount of days you spend in the U.S. needs to be tracked and if you go over a threshold, all of your worldwide income could be taxable by the U.S.4 - Selling real property means up to 15% of your sales proceeds might not be available to you for years (FIRPTA)5 - Lots of nuance at the state and local levels, which both want to take as much money from you as possibleMain takeaway here is that you should find a U.S. based tax person.

I used the proceeds of the primary residence I owned in NC to grow a portfolio of value add buy and hold here in College Station.

And to use all of the net proceeds in the purchase or purchases. 

Your sibling can use a 1031 exchange to defer capital gains taxes on the sale of the rental properties by reinvesting the proceeds into like-kind investment properties.

Honestly, and not to bash, but with the experience I have from our local REIA....I don't believe in the National REIA model.

However, this is not a cash out refi.Cash out refi is when you refinance an existing loan, with another one (i.e replace the loan) where there is enough money left over at the end of the process where you can put some proceeds in your pocket.When it comes to your strategy - just make sure you're being conservative with your numbers on the purchase / rehab if you don't plan on using other proceeds to payoff the HELOC. 

the property’s rehabilitation is scheduled for completion in 2025 and the rent will subsequently increase, can I proceed with a cash-out refinance based on the current rent roll?

I have yet to get a response as to how to proceed.

So if I understand this correctly, by qualifying to extend the 5 year rule to 10 yrs, $250k if single or $500k if married of proceeds from this sale would be exempt from capital gains? 

And you must use all of your proceeds ($300K ish).