With regards to rescue hams, I frequently see hamsters listed on gumtree that can only really be regarded as rescue hams, as they are evidently unwanted by their owner and are frequently living in totally unsuitable accommodation. If listed as being free to a good home, then they are in danger of becoming snake food. It's not unusual for them to be really quite young - sometimes only days or weeks out of the pet shop - before their owner realises that the kids aren't interested / they're more work than they thought / they're going on holiday / something else equally indicative of responsible pet ownership.
Unfortunately, I suspect that in a few weeks we will see a post-Christmas glut of such hamsters
