[amorphous]

What do you want to gain from this? How important is compensation?

If you want a full-time job to see how life at a startup compares to a more traditional work environment, four months are not enough. You'd need to stay at least a year or two because only then will you have acquired sufficient responsibility to be in a position where everyone else on your team depends on you and your output and what it means to deal with the pressure of deadlines and so on.

If compensation is not that important or your objective is to work with lots of new technology or build stuff from scratch, offer non-technical entrepreneurs to build their MVP. Depending on your experience level and feature scope you may be able to implement a prototype in four months.