The mirror modifier is what you need to halve your work time.
By example, i made half of a model, and went the other half to be the mirror of it.
I want the axe of the symetry to be what i made in red :
So i select this edge, click on Model -> Snap -> Cursor to Selection
Then i go to Object Mode and click on the " Center Cursor button"
this move the model origin to the cursor (that i “snapped” on the edge)
The origin of the model is what will be used by the mirror modifier to determine the center of the symetry.
I add a mirror modifier, check that the Axis is the one i want (x/y/z) i see the result immediately then proceed back to Edit Mode :
Now everything i will work on the original side will be automatically done to the other side as long as the mirror modifier is not closed or applied.
So for your model it means when you will extrude a leg, the other side leg will be extruded, when you will scale it, the other side will be scaled etc…