I read this Q and A as I searched for ways to fix my poverty in Pokemon Pearl. I know the games are sort of identical but I'm not exactly clear on just how. Need money bad! Here's the conversation somebody else had here on this site and I want to know if I can do this in Pearl? :
A fast way in diamond is to re-battle trainers
There are two retirees on route 212 outside of the pokemansion on the left side of the left wall. One is a man the other is a woman. Using Vs. Seeker you can battle them. They only have one Pokemon each and are relatively easy to beat. You will recieve $8000 each
(if thier Pokemon are Lv 40). And if you have a money boosting item such as amulet coin the amount is doubled.
Therefore from 2 short battles you can earn $32000
