one thing is your lending your money way under what private money should charge. unless your just doing your friends a favor..

Can you send the money to escrow instead of to the builder? 

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 will add that to your question of 10% or 20%, you need to ask yourself whether you need the cashflow or not. 10% down would leave some money with which to buy more properties.

The biggest question you need to ask yourself is if you are doing this to afford a property you otherwise couldn’t afford or to save money period, that will lead to very different conclusions about where/if to buy. 

We all assume this isn’t a house you’d buy with your own money.

It also appears Investor's Edge may have rebranded from their old company name "Do Hard Money".Propstream screenshot:"Investor's Edge/Dohardmoney" screenshot:

(Others would be more boring and say it’s just my money earning money.

Their ability to recover their money should you default is much lower in this position.

I would, If in this position, take the equity in the form of a HELOC and purchase a cash flowing asset that would not only pay for itself but pay for the cost of the money while putting cash into my bank account each month.