My wife and I are coming up to the end of a two year lease on a property in Northern Virginia -- as we've been here, we've noticed that our kids have had persistent respiratory issues -- particularly our 10 month old son, who we took to the emergency room at 4 months old, with respiratory issues (we didn't think to check for mold at the time).As we've been in the house, the owner (who regularly cut out the property management company he had been working with), has mentioned that when he lived in the house, he had noticed 'pin hole leaks' in some of the pipes.. and when we pointed out a 1 inch diameter 'soft-spot' in the kitchen ceiling, he chalked it up to that. 

There are cracks in the foundation on all sides of the house, ranging from a hairline to 1/2 of an inch.

I would say probably don't do either because once you give an inch they will take a mile.

I am concerned because it looks like the cracks include a shift of about an inch or so but I have zero experience with these things.

It's a 100+ year old home and has a drop of nearly 6 inches on one corner, 3 inches on another, and 4 on a 3rd. 

The most recent is that I should have put that their grass is not to become higher than 4 inches.

Once you know the flood elevation, it may be able to get out of the flood plain just by raising the height of the foundation several inches higher. 

I feel if I offer up information I'll be guaranteed the just value will inch closer towards 185k whereas if they have to figure it out based on comps, it may not.Thanks for your input.

That is going to be a tall task in my location as it is very hard to find any single family homes under 100K. 

And then filled with 6 inches of stone , then concrete with rebar .