Ye to get 500g/m2 will most likelly take 1000+ W lights and a SoG from clones not seeds with most strains.
From seeds you can grow about 8-10 plants max I would say that MIGHT get u close to 500G if u can keep canopy even and light it very very well.
But... from those you natrually get clones to make a mother or two for you next grow and then u can SoG 20-40 plants on a square meter and if managed (and lit) well that will get you around those numbers without going to extremes such as using CO2 enrichment.

Puffzter