I think income from this will depend how good is it going to be. There are few levels of difficulty here:
Level 1: Characters looking as AFK users
Level 2: Characters running around towns, teleporting, logging in, logging out
Level 3: Single characters farming
Level 4: Farming party
For even lowest level you need to handle receiving messages, mails, party requests etc but that is easy. Imo it is not worth to spend so much time to make single farming characters with so good AI that normal player wouldnt notice.
You need to consider:
- Changing the location of the character - not like pathfinder but like a real player
- Reacting to pms, pvp, cursed weapons
- Running away from stronger monster?
- Random stops, delays
- Going to town for rebuff
- How will they act just after grand opening?