Well, based on habitual spending, what I would like if I had a little bit more money, and what would sustain me, and potentially allow me to invest and get a good return on the money, I would go with $750,000,000 USD. 1/3 of it would be spent on buying land and building a place to live on it (and potentially have a retail and housing investment on it, if it is near enough to the city), then the rest would be spent in investments (most of it), and helping my family and closest friends get out of debt, and allow them to have their properties and such fully paid off.
If you mean money for retirement so I can stop working then I can settle for a million USD. That amount can tide me over until my old age considering that we already have our own home. We live a simple life, not much expenses with food and our only luxury is our foreign travels. I guess that amount can let me enjoy life to the fullest until the end.
An income of 2 or 3 thousand (USD) a month would be good, and even better, 4 or 5 thousand. However, at some point, the money would become more about luxury than just living a decent life (assuming there are no children).
I don't have any "debts" or credit, so in that sense I am "free", and it is a nice feeling.
I live by a rule : If I don't have the "cash" , I don't buy it. Instead of using "credit", or making
payments, if something I want costs more then what I have in on hand, I start saving, making
a small payment to myself, once I have made enough "payments", I have enough to buy the
item, but never end up owing any one.