It's an interesting question. but if you are an old hacker in the US or probably anywhere else in the developed world you qualify for a retirement income. At age 70 it would be something on the order of $2500/month. If you had an unmarried old lady, you would have something on the order of $60K per year plus reasonable health benefits in a few years.

The real problem is shelter. It is probably very difficult to build your shack anywhere near civilization, because of building code restrictions. The minimum, cost is probably some kind of used RV. You could theoretically avoid the code restrictions, because you could drive to a waste pumping station, etc. However if you blend in to a rural community sufficiently to be considered an asset rather than a nuisance, say by continually improving you property, you might get along quite nicely.