I also recommend a decent filter mate. Def pay that little extra for a good brand one. If you are struggling on the cash side of things atm, you can leave out the filter for a good couple of weeks yet remember.
Metalic shiny tape for the of seals of your filter/fans. You want a nice airtight fit mate. Youl prob get clamps with the ducting, but they aint worth much imo, i could never get them to the desired tightness anyway, but i do put them on after taping up well.
Ive been into growing for a year or so now and never really seen any threads about fires, thankfully. But you may want to get a small houeshold fire extinguisher or two mate... you never know.
Does he really need to spend $100 on a tds and ec meter if hes growing in soil ? Decent quality soil buffers ph does it not ?
Edit*
Doh, just noticed Wbd has covered most of the points ive made already. Maybe i should read the thread before posting lol