evening all

some advise will be greatly appreciated please.
Ive been looking at the possibility of BTC mining but dont really have the funds to buy expensive equipment.
Really like the easy to use interface of BitMinter so am very keen to try this but wanted to know whats the minimum hash rate I need to be outputting to see some sort of return after electricity etc?
Would starting off with say a usb block erupter at 333 be ok or should I at least go for the one that gives around 1.6? The USB miners appeal to me more due to space issues.
many thanks