I remember reading somewhere that his only source of income was giving talks, which he does irregularly. As the @krapp noted (don't know why he was downvoted)

I remember reading somewhere that his only source of income was giving talks, which he does irregularly. As the @krapp noted (don't know why he was downvoted) he may or may not be in dire straits but he is said to care little about money to the point of getting himself in tricky financial situations. Kinda like the brilliant Computer Science/Math student who helps everyone else with their assignments but gets kicked out of school for failing too many classes--because he didn't bother to turn in assignments.