A lot of rogues usually advertise in trade channel
Below is a chart detailing what levels specific cloths drop knight gold and which bags need them as mats.
Lock-picking: Rogues of level 20 can complete a quest from their respective trainer to learn the art of picking locks. Lock-picking requires a set of thieves tools in order to use and of course a locked item as your intended target.
As you level your lock-picking you can open different doors, lockboxes, and chests. Players may ask this service from you as a rogue and it is usually a good idea to ask for tips when opening lockboxes but you should not make it required.
Tips are always appreciated but should not always be expected as there are poor players without this guide out there.
When you are opening a chest for your group make sure to have auto loot turned off so you do not pick up loot which may not be yours and save yourself from others being very upset with you. Lockboxes can be received through pick-pocketing oozes or humanoids and also through kills.
A lot of rogues usually advertise in trade channel of the major cities which lockboxes they can open for players and say tips appreciated but not required. This is a good way of making friends and a solid profit to line your pockets with gold.
Here is a chart for a brief look at lock-picking skill progression.
