I'd warn against buying very very cheap necks / bodies from unknown manufacturers - you may end up with issues that would make the whole project bass unusable / worthless in the longer term. I bought the cheapest fretless neck I could for a project and ended up giving it away as a freebie because the heel wasn't cut properly, fretlines were already cracked and I couldn't sell it on for any money. Warmoth is expensive but is a recognised name..... That all said, if you just want to mess around with a cheap kit, nothing wrong with that!