These are professionals and they know the laws and also if a tenant has an accusation of theft you can completely wash your hands of it as an eviction company handled the set out(Not you and 4 of your friends). 

Which although your current mortgage payment is slightly higher than your rental income, it is probably a wash because of the selling costs associated with unloading your rental.

What if your contract says the buyer (now me) agreed to wash the sellers car for the next 5 years?

It makes no difference, it’s all a wash.....your depreciation basis will be purchase price Plus (or less in case of a credit) closing costs, Plus improvements.

You can also try to verify if the son had a prior living arrangement - or was he always living at the home? 

I've seen  reference to prior fire damage, violent crime, warnings about lead paint, etc.If it helps you sleep at night or you feel some type of personal obligation you can warn them.I would just wash off the eggs.

And oh yes, I really enjoy seeing five similar pics of the same small concrete patio that hasn't been pressure washed in fifteen years.

It looks like that water may be from someone failing to dry their hands after washing them

After taxes it is essentially a wash.

I have a park like that where we use the well for landscaping and washing cars, but the city water is connected to all the homes.