They did not even sweep the floors, the appliances which they received brand new are now filthy, shower has growth from moisture and the windows are dusty with dead flies on window seals.

I was able to get under the house and look around. the front foundation wall is bowing badly and in poor condition with moisture getting through.

HelloFrom the pictures I would have to say its moisture from the bathroom.

When I have a situation with mold, I first eliminate any source of water or moisture. 

So, my floors have been a concern due to moisture and cracking.  

Carpet is the cheapest and will look fine, but if there is any chance of moisture down there I'd avoid it. 

Placing them properly as well as resealing when necessary will deter moisture and water issues in the future.

Some parts had turned wavy because of moisture I think?

My only caution with laminate is that moisture/water will damage it...so keep away from wet areas.If you do replace with new carpet, make sure there is a clause in your lease requiring the tenants to have the home professionally cleaned when they leave....or there is a charge to do it for them.Hope this helps!

I havnt seen any water but I am afraid to do anything like carpet until I know if there is moisture.