Thank you for rescuing this kitty! Good luck getting him in the "trap." It can be very tricky! Sending "capture kitty without any trouble" vibes!
If your mom wants any information on socializing feral cats, maybe you can print these out for her?http://straypetadvocacy.org/html/soc...feral_cat.html
Obviously he'll be scared in a new environment. The most important thing is that he is confined to one room initially. He'd need to be in a separate room, probably for some time. A guest bedroom or a computer work room are perfect. But it has to be some place that you or your mom (or both of you, or whoever) is willing to spend time doing stuff. Ironing, reading, working on a computer, knitting, sitting and watching TV - whatever. But your presence is required for kitty to get used to (all of) you.
Again, the other ingredient is simply time. The socialization process begins by ignoring kitty but being in his presence, and providing him/her hiding places, a clean litterbox, food, and water.
Just remember, Cats are not genetically programmed to make people happy. They are genetically programmed to keep watch over their territory. So changing a cat's territory is traumatic to kitty. Their initial reaction is fear - they don't automatically understand they're being "helped." And their territory will be the box in which they're hiding. As they feel safe, they will slowly expand that territory. But under-the-bed (or desk or whatever) may be kitty's territory for some time. He'll venture out for food, water and to go to the bathroom. But until he's learned that the human in the same space with them is not any kind of threat, he may keep to a very small territory. The more he trusts, the more he'll expand that space.
Our feral rescues (rescued as kittens) did not like to be petted - which we never understood. It made them purr - but it was like they didn't want to enjoy themselves. Now that they're four, they can't get enough of a brush, and having their cheeks petted almost all day would be heaven. But it was something that literally took years - even though they'd sleep in our bed, rub up against us, and generally enjoy being with us from very early on.
Good luck - and keep us posted!