If using polyiso or extruded polystyrene (exp)  not expanded polystyrene) will give you an air barrier and moisture barrier if the joints are full sealed.  

Also if you file jointly you can qualify as a Real Estate Professional and take the losses - read more about that in BP Blogs.

There is a law that allows spouses to elect to be taxed as a joint venture if the business is not operated through an incorporated entity like an LLC.

We file jointly.

If your LLC does not file it's own tax return then all activity of the property was reported on your personal joint tax return. 

You need to pull the current deed and determine if they held as tenants in common or joint tenants with the right of survivorship.Also the use of quitclaim deeds very much depends on the location of the property.

*Replace needed plumbing parts*Use hardi backer or green boards for walls, make sure all joints and screws are covered with red guard or smiilar water proofing material, adding plastic sheet between the backerboard and the studs will give extra moisture protection.

As far as the mechanical work goes thats all on him. he will be piping everything to code (hopefully). if he asks you what type of material you would like to use on this project copper is best for water lines as for one copper joints are stronger than plastic and two copper is natural so your not drinking something that was sitting in plastic for god knows how long. now a days the go to is pex which is fine and also cheaper.

Of course having never done one of these before we do not know the proper parlance with these things. is it common to just blast out the deal to our buyers and say something like "We do not yet have this under contract, it is a joint venture deal, call/email us for more details" and then put it under contract with this other wholesaler?

The exception is if you are investing with a partner you should have either an LLC or a joint venture agreement.