Two builders are currently constructing single level homes with basements, Wonderland (http://www.wonderlandhomes.com/) and Boulder Creek (http://www.livebouldercreek.com/). I actually live in a Wonderland ranch home and highly recommend that builder. Hit me up if you'd like to take a look around.
Best of luck!
Keller Williams Advantage Realty
Here is a website to a map of that particular rail line.
Green Valley Ranch has new construction which is very close to what will be the 40th Ave. / Airport Blvd. stop on this rail line. Oakwood homes is a primary builder and has ranch styles with that square footage and basement.
Please let me know if you need further help.
Darrick Kizlyk - Realtor
EXIT Realty Denver Tech Center