If he has no intention to link between the sites I see no problem to have them on same hosting, although shared hosting is the fastest service on the earth :-)
I have seen wire transfers to go through 3 intermediary banks before reaching its destination and that costed close to $100 so, yea this is the only reason. You should better check with yout aff. program whci his their correspondent bank and check in your country which of your local banks words...