[dlgosuqv] Payment for instruction long after

Teach a workshop for free, but take down contact information.

Periodically (perhaps exponentially rarely) after the workshop, you ask students to voluntarily contribute money if they found the workshop useful later in life.  Include a syllabus to refresh what was covered.  It may be a long time before the effects of the lesson finally click, and only then should a student feel obligated to pay.

Might work for a dance lesson.  Of course there will be free riders, but maybe not so many if you earn good will.  It seems a more honest way to ask for money rather than "collect money before", which makes the students bear the risk of poor instruction.  It also helps even out those who have more or less ability to pay.

The instructor gets feedback on how well he or she did.

Somewhat related: Delayed compensation