@Martina PollardHi Martina,On the surface, this sounds like a great opportunity.  

That looks like common surface mold due to lack of ventilation.

I know they make marijuana smoke detectors as well as surface residue detection tests.

Clear, constructive communication should bring more facts to the surface that you can then work with.

Renovated all apartments, converted M2M tenants to annual leases, instituted strict rental criteria, implemented online payment portal, invested $75,000 into leasehold improvements (HVAC, drainage, exterior paint, concrete.)

@James E.Hi James,I'm not a wholesaler... just an investor who has dealt with wholesale deals.My broad perspective is that wholesaling is a marketing job - where the wholesaler (on the surface) is trying to help a seller, but ultimately is trying to do that in a way that ends up costing the seller more money than it should have, had the seller taken more traditional means to achieve that sale.  

Visible dirt/dust on almost every surface, trash (including Q-tips) left on bathroom floor, toilet not cleaned, food splatter around kitchen, smudges on walls, windows and mirrors, list goes on... 

We were helping a friend renovate a house which had been home to a heavy smoker: one room was so bad - owner had smoked in the same chair for 30 years - that we had to replace the sheet rock on the walls and ceiling.There have been some studies in the past few years showing that the chemicals from cigarette smoke, even when encapsulated with paint, eventually come to the surface exposing future residents, in particular young children.  

I have been trying to find if there is a wall assembly material that can act as stuctural, shear strength, insulative, interior surface and exterior surface.

Once you rehab it and maybe put $50k of "sweat equity into it", it would be worth $200k, but they would sell it to you for $150k seller financing after the down payment.So, on the surface it sounds great because you aren't coming out of pocket, but in reality if you have the means to close the deal in cash or with any kind of financing like a hard money loan you would likely be better off.