Whether bank or credit union - either will work. 

Take out an equity line of credit on the property that can be sides as the down payment for the primary residence.

Dedicate one checking account and credit card exclusively to real estate.

For me as well as the seller.First, you have to define Sub to financing.Do you mean the reckless kind where you overpay for a property, take over the financing and borrow from others to cover closing costs and holding costs when you have no money, no credit, no income, no reserves and can't tell a warranty deed from a deed of trust and you close on the kitchen counteror do you meanbuying below market value, already having a nice income, having reserves, using escrow and title, already understanding the due on sale clause, have done a lot of creative purchases and know when to use and when not to use creative finance and how to recover if something goes amiss?

Take a look at the overall picture, i.e. credit score, debts etc.. to make a decision.

Or are you actually talking to a bank about buying the note so you can see the notes and credit on the owner of the property?

They have no credit history, so you have no idea how responsible they are financially.

When you go to a Bank or Credit Union, they can only offer you what products that bank or credit union offer. 

Shapiro are tacking on the STAR credit (that they did not get directly) onto invoices for those residents.

Yes, but the 3rd option is I pay the remaining seller note principle in cash via my own savings/lines of credit.