So both have to be members but do they have to belong to the same resort?
both have to be members, yes.
both do NOT have to have the same home resort, no.
(if you own BLT pts and transfer pts in from SSR, the SSR pts retain their home resort and can only be used to book SSR at 11 months. at 7 months, the SSR pts can be used to book BLT.)
you may only complete
one transfer per year, either in
or out but not both.
your
DVC contract prohibits accepting compensation (money) in exchange for transferring pts, so if you say or imply anything about money changing hands to MS, the resultant lecture is your own fault.
most transfers are done by the transferror calling MS and giving MS their account info and then bringing in the other member into the 3-way conference call.
once the pts are gone, they are gone. you won't be able to get them back. (on the bright side, you won't be responsible for any reservations made with those pts once you have transferred them out.)
also, banked or borrowed pts may
not be transferred out. (but pts that have been transferred in may be banked.)
(naturally, banked or borrowed pts may still be used to book a reservation that can be rented out.)