Thanks, but I am still confused. Both you and Joepistole know and understand the details much better than I do.
Come now Billy, false modesty does not suit you.

You know I am far from being well educated in economics. Pandamoni is a Wall Street banker, highly intelligent, but doesn't seem to relish correcting mistakes made by amateurs such as myself and others here. one_raven is (or at least was) a vice president at a large Atlanta bank, I inferred CitiBank. He seldom posts also.
(1) Main problem is that to make the second loan (mortgage) the bank must have actual cash to give to borrower
Sorry for taking so long to respond to your post, but I have had an eye problem that prevented me from spending much time at the computer screen.
Most of the banks transfers are not in the form of 'actual cash', but electronic transfers from their balance sheet. You know the physical cash in circulation is only a small percentage of the total money supply. Just as the banks do not keep cash on hand to offset all savings invested in the bank, they do not keep cash on hand to transfer to the seller of the house. They electronically transfer proceeds from their balance sheet to another banks balance sheet. No cash changes hand in the process.
#2. I have been assuming that it why a secondary market in which they can sell mortgage #1 must exist. I do not see how either buying an insurance policy that mortgage 1 will be paid on time OR making some accounting shift on the bank's books produces the second $250,000 to give out to borrower
OK, Billy, the following is my assetment of the situation, which could be wrong. The bank CAN sell the mortgage on the secondary market, most likely to then be packaged into a MBS or similiar. But most banks don't sell all their mortgages. That is where the Credit Default Swap comes into play at the individual bank level, in addition to the secondary market level. The bank can, and usually do, take out a CDS on the mortgages they hold. The mortgage is then considered to be 'protected', having no risk of a default causing them to lose money if the mortgage is not paid. The bank still holds the original mortgage as an asset on their balance sheet, as it represents real value (the property itself). They then transfer the
liability for the mortgage 'off balance sheet', since it is not supposed to pose any risk of default. This gives the bank an additional asset, the value of the physical property, upon which they can borrow funds against from the money market. The bank can borrow money at a lower interest rate than the interest rate they charge consumers. The difference in the interest rates makes profit for the bank.
The place it comes from, which I call the "secondary market," will want something in exchange for supplying the second $250,000 - That is why they get ownership of the first mortgage.
Think of it like the home owner that takes out a 'second mortgage' against the equity in his home. The financial institution that issues the second mortgage does not get ownership of the original mortgage, but a claim against the equity in the home. By taking out a CDS against the original loan, that increases the 'equity' the bank holds in the physical property, since that property is supposed to be free of default risk. Now Billy, explain to me how you think banks can 'leverage' their deposits by ratios of up to 12 to 1 without such methods?
(2) A more minor problem is that I do not understand why the mortgage would be a liability to the bank and then become an asset when back by insurance. The real backing of it is the house. The firm that issued the credit default swap can fail, but the house will be there (or the fire insurance payment). The mortgage is a liability to the home owner, not the bank. The mortgage is always an asset of the banks as soon as the borrower signed on the dotted line. – It can be sold. To my simple POV, what you are telling me makes no sense.
The bank has a balance sheet, with assets on one side and liabilities on the other. A depost in a bank is an asset. When the bank loans out that money in the form of a mortgage, the 'electronic cash' is deducted from the asset side. The bank then has two entrys on its balance sheets, one 'asset' for the property value (not 'cash'), and one 'liability' representing potential loss (default) of electronic cash on the other side. The two entries balance each other on the books. By means of a CDS, that eliminates the liability since there is no possibility of a loss. This gives them a 'clean' real property against which they can borrow more money for lending on another mortgage. I am putting this in very simple terms, not considering reserve requirements for instance. By doing these Credit Default Swaps, the bank can leverage the same mortgage several times, making profits from the difference in their borrowing and lending rates. As I stated, I am no expert in these matters, but that is a simple explaination that may need to be corrected by someone more knowledgable. I won't even get into the more complex financial derivatives, but there are many of which I have little understanding of exactly how they work.