A private mortgage involves a sale, but a private mortgage is the loan associated with the sale, and not the sale itself. The sale of the property may not be particularly lucrative, but the loan certainly can be, especially with subprime loans that commercial lenders won't touch.
also assume you understand that this scenario increases the likelihood that the seller is the one left holding the bag if the bad credit purchaser defaults.
Buyer/borrower defaults, lender/seller forecloses and sells the property again. Seller isn't holding the bag. Seller is holding the house.
Hog farm
You keep talking about a hog farm. Under my scheme, to avoid the higher non-occhpant tax on residential properties, you would have to rezone. I've never found anywhere that will allow you to rezone from residential to agricultural, so you'd have to go to commercial or industrial to avoid the residential tax hike, but the property taxes on commercial and industrial are considerably higher than residential, and both are currently declining in value. Out of the frying pan, into the fire.
Doubling property taxes doesn't get you the result you want either. It just hurts the small owners, because property tax doesn't care how many properties you own; it only cares about the property to which it's attached. Large corporations don't care about a doubled property tax, because they can just eat it and raise the rents
Tax rate isn't just doubled. It's statutorily increased so long as owner occupancy rate is below 85%. To keep their margins, they will need very high rental rates and very high occupancy rates, and those two are inversely correlated. The higher the rent, the more pressure they have to buy. Meanwhile, all these former landlords are looking for someone to put on a deed so they can save on their taxes.
Such a tax will decimate returns on institutional investors. They'll jump ship quickly, throwing their dollars at the next highest return.
No, the investors who stay in the industry will turn to private lending, or convert their rental units to condos, which can be sold instead of rented.