Actually he said the Viv is 24" x 18" which would be big enough to house 2 Leos. I'm not sure about dividing the tank, in my opinion the sections would be a bit small. I know people say they divide 20 gal long tanks to house 2 Leos, but I would never do it, but then again I wouldn't keep an adult in a 10 gal either LOL The smallest tanks I have for single adults are 15 gal which are 24" x 12".
Housing a single female with a male is not a good idea. Yes, he can stress her out by continual attempts at breeding. And with that, are you ready to incubate eggs and raise a whole bunch of babies? It can cost a lot of money to house all those babies & care for them. They don't have to be 18 months old to breed. Recommendations are basically, at least 1 yr old and females should be a minimum of 50 grams in weight but 60 grams is even better.
And don't forget even if you did get a female to house with him, you still need to quarantine her for at least 60 days to help be sure she isn't sick or carrying parasites. So, you would need a 2nd enclosure anyway.
-----
www.StoplightCityLeopardGeckos.com