I know someone who has sold multiple houses with seller financing, ie giving the buyer a mortgage. This person gets calls constantly from people who offer to buy the mortgages. Mortgages are public records. I have also seen classified ads seeking to buy mortgages. It is not a problem. But, to get FMV someone will have do some research on the lady's behalf, to find out what FMV is at that time and also find a buyer willing to pay FMV. This can get complicated. Say the mortage interest rate is 6%; how desirable is it, if the current rate is 3%? Or if the current rate is 12%?
Also, selling the note usually has no effect on the buyers of the house, other than the address to which the checks are sent, *provided* the terms are standard. Don't get a standard contract and then strike out all the clauses you think won't apply or you don't understand.
Several loans I have obtained over the years have been sold to others, no big deal.
Anyway, the value of money is an important factor. I too would rather get full value for the house at the time of sale and invest the money. Given that there is a plan for what happens after the assets run out, it seems reasonable that the lady may be able to tolerate a higher risk investment than a CD, so may be able to earn higher interest than a CD. I probably would put it in a mutual fund of stocks or mixed stocks and bonds. Mutual funds provide a lot of flexibility: you can take out exactly what you need, when you need it.
Una