I bought a 1960s 355k duplex with an owner occupied loan. 7.5% interest, about 2800 mortgage payment.

Considering a DSCR loan with around 20% down.

80% LTV commercial loan - 25 year AM with a floating rate of wall street prime.

I also have about $20,000 in student loan debt, though I expect it to be paid off by the time I move.

I agree with other responses here, and to piggyback on them it seems everyone plans to 'own forever' when they sign a 30 year lease or finance term, and then things change (job, relationship, life events, etc) and folks try to sell the property with 25-28 years left.Banks do not look at power bills when determining DTI, but they will look at a solar loan/lease. 

Tring to get a 100% loan is probably very unlikely without significant experience and is also probably unethical. 

Mortgage: The deed reflects ownership of the property, while the mortgage reflects liability for the loan.

Borrowing: If you have an investment or business that makes more money than the interest rate costs you on the debt, it might make sense to get a loan to multiply your returns.

The home sold for 135k to an individual using a VA Loan.

Balance sheet and depository relationships (some banks requiring upwards 10% of loan amount) are being prioritized over merits of the deal/collateral.