Just to clear Serendipity's name here, she jokes around alot and has the best heart. She is the first person to help people out and will give you the armor off her back (so to speak) for a friend.
As for porting fees..50 plat is a nice donation
[You must be logged in to view images. Log in or Register.] When I port people for donations, sometimes I get very lucky and get around 10-200pp. I never would "Charge" for any mana use, but some people are just very generous like that.