Legally you can claim estoppel and latches as a defense as they let it go on for so many years and you relied on it when buying. 

I'd be surprised if the way they are teaching & doing the lending is legal. 

The good thing about househacking a legal multifamily unit is that lender allows you to use the vacated units of 75% market rent as an income to offset the potential current mortgage.

Is it a legal 3-family on the city card?

I'd be happy breaking even just to get the equity on a building, especially since I'm currently renting - aka giving my landlord wads of cash every month to buy new sports cars. 

I don't think it will be as simple as trying to just undo what the last owner did; you're going to need legal descriptions of each lot and that generally requires a survey. 

What about legality and insurance. if using a single family home wont the town shut you down (especially if neighbors complain) also will i need a commercial insurance policy?

When you're on a temporary visa, especially without a clear path to permanent residency, the risk involved can be substantial—both financially and legally.

Now, each lease will be unique, so you can't apply this across all commercial leases, but commonly, LL is responsible for exterior and structural components, while tenant is reponsible for any interior items.How to best explain this: honestly, I would request the tenants have their own legal counsel review their respective leases.  

sounds completely legal, maybe my friend is crazy and he wants to lose $900,000 There is transfer tax and property tax.