It never hurts to check both the EXIF and IPTC section of a file to see if there are any comments, copyrights, company names, restrictions, etc... but just because there isn't any info like in the metadata areas doesn't mean that they weren't shot by someone who won't take too kindly to the idea that someone else is doing something to images they hold copyrights to.
I prefer a per image fee personally and to outline specifically what it would cover. I think charging an hourly rate would discourage me from learning to work faster and better
For instance - .25 per = color correct/boost/reduce and adjust for under/over exposure as much as possible. I think that's reasonable but a client may not. I have
very little paid freelancing experience but I'm confident I could go lower than .25 per and still get through them (1000 / 700MB CD limit = 70KB avg file size) in an amount of time that would make me quite happy

Doing more than that (like cropping and retouching) I think I'd ask them to select a few of their favorite files and go from there.
Like Doug Nelson said, these are likely proofs and not print-worthy files.
A Nikon D2Hs SLR will give an average file size of 1.65MB per with 4megapixel sized files (quick math from a sample of 40 files I have from a project - not my camera) My sony point and shoot 5MP gives me file sizes around 2MB per roughly at it's 5MP setting. I found one image I have that is about 82KB and it's pixel dimensions are 1000 x 768. Theoretically good enough for a 4x6 print size or going to video IMO but nothing larger. I've some 10MP images from a canon EOS-1DS at around 2MB+ per file but I don't know that that could be taken as an average size - the sample pics I have from that camera at that size are few and underexposed.
Just my two cents... and maybe someone will tell me I'm way out of line with my way of thinking