My thought is I buy a multi-fam (off market preferably) and house hack for 2 years then move south.

From a practical standpoint, since you were already in the process of buying the property, it's probably too late to bring in another lender before the end of the purchase.  

Maybe people buying and not fixing up who just want a multi unit at lower price point?

DSCR requires No income, No Taxes and Commercial requires a PFS, occupancy ratios usually above (90%), Credit scores above 720+ much higher assets for (PITI reserves and overall risk, landlord seasoning, and more.A Heloc can be used in most cases for anything but when you are trying to buy a commercial building which is higher risk, the committee/UW can and in most cases will deny it if they feel you are over extended low assets or with no landlord experience, unless you have a meaty amount of equity to cross collateralize for a junior lien on another property.

Our long-term plan is to eventually move out, rent both units, and buy a house of our own.

@Cliff Durrett Just buy at the auction.

I'm planning to have a separate bank account/accounts for my entire portfolio, just wondering if anyone has recommendations for software to use as someone who'll have buy-and-hold and will be working with a property manager?

Still not sure it makes sense, but worth a look.If you want to be green, just buy a green energy plan from your electric provider if you have a choice of providers/plans.

My current tenants of 4 years have asked to buy it.

As a new property manager I’d like to be on top of that if someone asks me, what I suggest would look the best and be the best in their rental units.I had an awesome property manager who would buy the modern nice looking flooring in bulk so when his owners needed to rehab a unit he sold them the modern vinyl plank flooring for cheap.