Reply #3: No, DEMAND a consultation fee.

[liberalhistorian]

Politely, but firmly and unequivocally. Advise that you will NOT BEGIN ANY WORK on the questions until you've received at least half of the fee. If they refuse, simply refuse to answer any of the questions. You don't work there anymore and you are not obligated or required to do anything they ask. If they're having trouble with a program or anything else you worked on, that's their damned problem and they should have thought of that before letting you go.

I've had that same problem after being terminated from positions. One boss got rid of me before realizing how difficult and involved some of the files I was working on were and went nuts trying to figure them out. When she called to ask about them and refused to pay me for helping out on them, I told her where she could put it and never looked back.

You are NOT NOT NOT NOT in ANY way obligated or required to do ANYTHING for employers once they've let you go. What can they do to you if you refuse, they've already gotten rid of you so they can't threaten your job. If they won't pay you, politely refuse any assistance and don't look back. And be firm about it.