Well... It is mostly personal preference... They should use the money the make to volley other and make even more money. They can technically just use it to convert to tier three or to buy the next dorm. The Helper _Warrior
I like to volley them to 900m. The. Depending on how much money they have, I volley with them to around 50m. That's enough for 10m for 13th dorm, and 48m for 3 t3 members. (small town goddess an nursing student). They will then have 6.7k cs at 900-950m. Underpriced still, so I'll volley to 1.1-1.2b and sell. That leaves them with 5-10m left over
I use 3-5 1m tutors an have them volley to max until all of them are 50m. You end up losing about 80m when you drop them, but you make around 300m in the volleys. So it's worth the sacrifice.
Jaccky: I did this today. Here was my results. Volley from 1k to 800m. Then volleyed with the tutor. I bought 3 1m tutors and volleyed them to 75m. I made 10m on each small volley, dropped the three for a total loss of 60m. My tutor upgraded to 6.7k cs and then I vollied them to 1.3b and sold. I made a total of 200m.