how should i do this?

ok so someone i talk to builds reptile enclosures, he said he could build me a 6x4x3 (lxwxh) enclosure.

how exactly should this deal work? ive never had this done before

Uhh. He builds it. You pay him? Not exactly sure what you're asking.

Sounds more like an addition than an enclosure.

What do you want it for, will it be at all useful to you? If so then set aside the money, have him build it, and then buy it from him for the cost previously decided on.

sorry. like.. should i pay first? contracts? is their supposed to be some kind of warranty?

details? ive NEVER done this so im clueless

EDIT: its for a tegu (for when he is bigger) i dont have one, but im planning on getting one in november.