well it can cost ya 3-6k but depends how pro you wanna go my setup i can grow up to 15 small plants an yeild between 1-2 oz off each plant so on average bout 15- 30 oz per harvest an my setup costs are as follows
600w hps light an ballast= £120/$240
extraction fan= £50/$100
intake fan (optional but rec)=£50/$100
pots an light hangin kit/ extras=£50-100/$100-200
i built the enclosure myself. you can shell out for a cab to be made but they are expensive an u can convert a cupboard easily enough.
then all i buy is seeds or u can keep a mother
it really depends on how u wanna grow do u want to keep it simple an have lots of smaller plants or more complex an have the plants to their full size an full yeild but you would need a whole room for 20 plants of that size
if its for personal use you should keep it simple an a setup like mine will do you justice if you wanna make dolla then you should go all out an spend 3-6 k
i personally wouldnt go hydro for personal use not un till u get some experience but if u want to look at one of the WILMA kits available as they are easy to use an affordable