I’d love advice on leveraging my existing assets, navigating seller finance deals, or other tips for scaling effectively.

The macroeconomics are on fire here - population growth, job growth, and companies moving and developing here.

Some things have shortcuts, but developing relationships isn't one of them.

As the new owner, you’ll want the lease and your landlord insurance policy to take effect as soon as you take title to the property.Temporary Lease Considerations:While short-term leases can work well, leasing to a seller long-term often leads to complications.

As others have said, the best thing your son can do is run far from this deal, buckle down, save his pennies (he probably already is doing this), house-hack, and improve a property with sweat, hard work, developing a DIY skillset, and self-managing tenants. 

Stessa is not perfect but I like the capability, love the %5 interest rate on my associate account and have found the support honest and effective.  

Looks like is passed in 2022, effective this year.

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.

We’re developers managing our own portfolio and don’t have any outside investors.  

As you are finding out, it is so local that the next door building effects your investment.