Even if I had the time to do it, I wouldn't make french doors. I've bought them for as little as $130 and as much as $170 per door (from Mitre 10 and Bunnings).
I don't know about you but it would take me more than a day to make a door. Then there is the cost of the materials if you already have the tooling (router bits or shaper blades).
You do the math.
If I were you I would concentrate on more cost effective jobs.
Doors are a standard height of 2040mm. You need another 30mm to allow for the head of the jamb and clearance below the door. Maybe more depending on the floor covering. Its probably not a problem with solid doors as you can trim them easily.