And you'll have a solid W-2 income to help you qualify for loans. 

I own a mortgage company, so I have my loan officers use this Fannie Mae income calculation tool for all business for self borrowers: https://singlefamily.fanniemae.com/applications-technology/income-calculator .

I'd need the interest rate to be roughly 5% to breakeven on an interest-only loan, and was considering a balloon payment in 5-7 years.

Through a hard money lender, but I will take out a DSCR loan in March to refinance.

If you are getting a loan no there is no way to protect yourself from crushing your credit or having a foreclosure against you if you are the borrower. 

We have secured a home equity loan against our home (which we own out right with no mortgage payment).

I've also assumed VA loans where little cash was used (seller had low/no equity).

I believe the investor may need a commercial loan at that point or could do 3 separate loans since they are on different parcels.

Mortgages are the last thing to default for a homeowner and appreciation has been so high in Canada that every homeowner who has purchased before 2022 has gained equity and could just refinance their loan over a longer amortization before defaulting.

I can help run their existing numbers to get more of an idea of the Business's Financials and work with you on how a loan payment would affect cash flows.