Hi Lisa and welcome to TP.
I've never heard of an EOS 300S. There was the original EOS 300 (1999), followed by the 300V (2002) and the 300X (2004). Maybe you or someone else misheard and what you've been offered is the 300X?
It would be worth checking. The 300 had a plastic lens mount which might not be very durable. The 300V and 300X had stainless steel mounts.
Anyway, is it a good buy? Depends .... The 300X is pretty new by the standards of film cameras so it will have fairly decent metering, autofocus, exposure control, etc. And it will take all the Canon EF lenses that have been made since about 1987 so you've got a huge choice there.
The only real downside is that it's a film camera. I think there's still a role for film, but to my mind digital cameras are probably much better for people who want to learn photography, for three reasons:
(1) it costs nothing to experiment;
(2) you get immediate feedback;
(3) the camera settings are stored in the image so you can see what worked and what didn't.
A digital body would be a bit pricier though. The EOS 300D (6 megapixel, introduced 2003) sells for about £120-£150
second hand on eBay. On the other hand that price differential only equates to a few rolls of film.....
