Essentially it's such low ampage that anything would do, but I'd like it to be compliant.I've been reading the code, and I'm making one alteration to make the installation an extra half inch from the roof deck (they were going to be 1.5" from deck, now 2"), but I can't find the exact codes for the wiring type.I have found some CL rated speaker wire in 18gauge, rated for 150v.

Tile over it.

Could be a number of things like improper install, wood shrinkage, framing deflection. 

Plus we decide case by case what we feel like doing.What we do ourselves (in general) - We paint both interior and exterior, hang and tape drywall (but on the last big drywall job we hired a couple of guys to hang the ceiling pieces), we fabricate and install trim, hang interior doors, install some flooring.

@Joshua H.Have you looked at ceramic wood looking tile?  

You can look at some items and generally say that a tile floor will have less frequent cap-ex replacement costs than a carpet floor.  

I will stay away from the ultra cheapo stuff but want to keep material costs below $2/sqft and will install myself.

Eliminate the carpet and drapes from your units- install commercial vinyl tile (NOT the cheap-assed peel and stick type!)

My Client wired the funds down to Stewart Tile in Costa Rica.

And when NOTHING will work it's necessary to make sure that you kept some decent sized pieces of carpet left over from the installation.