The key think to remember is that once you buy into the system, your main investment will
be in lenses, not the initial body. You can always get another body later and still use all the
lenses you've got for the system.
A 50mm 1:1.4 is a pretty standard "fast normal prime" lens. I'll break that down:
- Normal means that the lens has a more or less normal field of view. Neither telephoto
nor wide angle. On a DSLR it's a good lens for knife photographs.
- Prime means that it is not a zoom lens. Prime lenses are generally, smaller, faster
and optically better than zoom lenses. Of course they don't zoom...
- Fast means that the lens admits more light when it's wide open. This lets you take
better pictures in low light. It also lets you take pictures with a shallow depth of field,
i.e. where only the part you focus on is sharp and rest is out of focus. This can be
very useful once you learn how to use it. Of course you can close the lens down
for greater depth of field and generally increased sharpness.
A 12-24 lens is ultra-wide to wide angle. It's an excellent complement to the other
lenses in the set. Don't worry about it being off-brand if the price is right. She can
always replace it with a better one later if (1) it's not up to snuff, and (2) she decides
that she likes that focal length (I do, and have a similar lens in my micro 4/3 outfit).
I'd go for the used set if everything appears to be in good condition.