We've just pushed a patch update v1.17 that addresses XP progress from a start game state.
Players were experiencing an issue with progressing XP while performing sex acts and earning money from a default start game state. Starting XP Level was "0" and should have been initialized to "1", which resulted in a error earning XP and cash.
Patch v1.17 addresses these issue correctly initializing the default game state to XP Level 1 and allows players to earn XP and Cash as intended during intercourse. Additionally we've added a small XP bump increase to players during any position change.
Please report grinding progress and XP increase rate issues into our bug report, and we'll consider other areas and rates in which players can earn cash and XP to make the game play more rewarding and satisfying in future updates.