However, the HMRC (UK tax authority) does not provide tax credits on tax paid on US income under an LLC, therefore I would need to pay taxation to the IRS on US income, and then to HMRC which makes this structure tax inefficient for non-US residents.On the flip side, incorporating an LLP provides flow through taxation that is recognised in both jurisdictions.

I will continue to work as a Financial Analyst in Corporate America but my husband will be on the ground full time executing deals.

@Audrey Koerber @Chad Urbshott gives you good advise, find yourself an attorney and accountant with cross-boarder experience ... preferably in real estate.Canada does not have he equivalent of an LLC - essentially the simplicity of sole proprietorship with the benefits of incorporation - and the CRA will treat it as a foreign corporation {in almost all instances}.   

No one wants to be in corporate America forever but you have to focus and trust the process.

your share of income / expenses are reflected on the K-1.If the LLC agreement mentions that you are getting 10% of the income and expenses.You will see a net figure on your k-1 incorporating all the income and expenses.

I don't know if there's way to incorporate the equity into the 2% rule.

Trust me, I'm a CPA and work in corporate finance and  I've sat through a demonstration on this.You make a very good point about opportunity cost with the HELOC and it's a huge detractor from this method.

By incorporating in another state, Roofstock can somehow go around certain rules that carefully regulate brokerage activities carried out by local brokers in some states. 

So my question is, I thought salespersons working under a broker were able to incorporate bc they were like independent contractors under the broker?

Creating multiple LLC's limits what is exposed in the case you get sued.You may want to also incorporate an umbrella insurance policy in addition to the LLC's for your asset protection strategies.You do need a separate bank account for each LLC.