depends on how ur settin it up.. u can go head n buy a hydro system or u can bang it out walmart style.. end up with lyk $50 for a simple hydro system..
$30-80 for some good liquid nutes, dependin on how potent u want your stash to be.. and then u set for waterin..

lights can run from $50-150, dependin on if ur usin lights or not, and dependin on how plan to have the lights set up, and how potent u want your stash to be.

Easier to hide? depends on how you set it up.... you can set up a bin, trunk, closet, room, etc.. but the plants will stink, so that also adds to price, dependin on how much u care about the smell..

the more u invest, the better turnout you'll have, quantity-wise, quality-wise, and security-wise.. or if you plan ur money well, you could come up with the cost-effective equivalent..