If you need Radon prevention an active system is the best if it's going in the basement below the concrete slab. The passive is requires a visqueen layer that the slab sits on and it causes the slab to crack more.

IMO, properly cured concrete with plastic under it will have fewer cracks than concrete without plastic under it.

Some studies that I have read state that a double layer of plastic can result in less cracking because it unbonds the concrete which allows it to move with expansion and contraction.  Of course, there is still a need for the typical expansion and isolation joints.

I thought I would post an update. I have been doing alot of research over the last few days...Spoke directly with Endurablock, who verified that the house is indeed endurablock. The gentleman I spoke with was very helpful... could remember the exact location of the house I am looking at and was very familiar with the circumstances. He said he would have no reservations about the blocks. He described exactly what I should be seeing as far as the "spiderwebbing" I described earlier. All was described exactly as it should be
I called the bldg. inspector, and he said he couldn't come out to do an inspection unless we were the property owners. But he also was familiar with the property. He agreed that all the wood that is exposed was bad, but thought that most of the joists were ok and basement framing was ok.
So- today we put in a very low ball cash offer. I appreciated the insight from this post regarding the value of the property. Our offer was below the lot value. We don't know if the sellers will see this as an insult, but considering the circumstances, I think they should consider it. If they don't accept the offer, I won't lose any sleep over it. If they do accept our offer...Well....the next year will be quite the journey.

I will keep everyone on this post up to date...we should know more tomorrow.

Thanks again