Hey, I hate to tell you this, but you won't know it is a male until it grows to be about 4 inches long (!). Only then can you see the super long front nails + thick long tail ("male") or the very short front nails with tiny tail ("female").
And there really is no way to tell how old a turtle is unless you actually watched it hatch. You can prolly guess that it is less than 6 months, but you never will know for sure. Sorry!
Before you buy, make sure you read over the basic care sections on the main page
www.readerslider.com (scroll down & click on the topics). If you already know the "good" way to care for a turtle, then you will also be able to make sure that the pet store is taking good care of them too (by seeing what kind of tank set up they have them in) & hopefully be able to get a healthy baby.
FYI: the proper tank set up for baby RES is going to be a bit of an investment, but once you have the right set up, then it isn't expensive after that. The important thing to remember with turts is to "prevent" sickness so you don't have to pay lots of money at the vet!
Here's an example of what I mean:
20gal tank - $25
50W water heater - $10
floating basking area - $15-$20
UVA/UVB light bulb - $40
clamp lamp fixture - $20
water filter - $30
charcoal pad for filter - $3 or you can get a container of charcoal for $15
small nylon bag for making your own charcoal filters - $1
cuttlebone (calcium - good for their bones) - $2
container of Reptomin food pellets - $5
So an initial/basic set up (with no fancy stuff added) can cost around $160. It sounds like a lot, but the good thing is that most of the stuff doesn't need to be replaced all the time (obviously you have to buy filter stuff & food which isn't too expensive). And when turtles are kept in the right setup, they will be healthy & make AWESOME pets that can be life-long companions with minimal care.
