I probably understand what it is. It's like doing small tasks to get paid. It's quite complex and too specific niche so there is barely known script or theme out there. I know some of the features exist in certain plugin, like task maker can choose as many as employees he set before, and minimum withdrawal.
But it may be not in plugin itself but in their
addons of plugin, which means you need paying extra
try asking developer if there is a feature that is mandatory for your micro-job website, here I list some possible theme/plugin for wordpress that might doing so
MicrojobEngine wordpress theme helps you build a complete micro job marketplace platform. Fast, conveniently user experience & safe payment system
www.enginethemes.com
for plugin you need a listing plugin, try WP Job Manager its have some addons that purchased differently