Here is the full list of all 15 Prostitute Simulator achievements.
Meet your first client
Obtain the bunny skin
Obtain the maid skin
Obtain the bikini skin
Obtain the oiran skin
Obtain 1.000.000 yen
Obtain 10.000.000
Obtain 90.000.000
Get a client to hit you with a venereal disease.
Get pregnant and have children.
Meet your first woman client
Complete Act I of Story mode
Complete Act II of Story mode
Complete Act III of Story mode
Get 5 millon yen in one day