Any possibility of contamination form those?

Dry cleaners use some nasty chemicals and if any of that contaminated the ground you will be on the hook for it. 

Found this in My Texas Real Estate Principle 2 Book"TMARR requires that all persons who conduct assessment and remediation of mold be properly trained and licensed by the state.Under the rules, a person is not required to be licensed to perform mold remediation in an area in which the mold contamination affects a total surface area of less than 25 contiguous square feet.

Is the whole house likely to be contaminated with asbestos now?

If you are interested in MHP in North Carolina that is not on a City or County Public Water System then you can find out at this url  https://www.pwss.enr.state.nc.us/NCDWW2/   if it is already  permitted and can see if it has any violations and/or contamination in well source.  

If it's been leaking for years it could go down way in the soil.You would have to them keep cleaning out the soil until no further contaminants were found.

However your buyer will likely want to get it tested and possibly insured to cover any leaks and resulting contamination.

As much as I dislike insurance companies, I have to agree with the ruling, poor or contaminated materials is not a covered peril, pretty clear that this is a product liability issue.

most sellers are reluctant to allow sampling for fear they will be in worst condition if the buyer finds contamination and then walks. the other question is are you going to finance the acquisition?

For instance imagine if the site has some environmental contaminants below grade.