Have everyone sign new leases and park rules, and hold them accountable.As far as updating some homes: A good pressure washing job can go a long way. 

In your case it's about a wash, but in reality you're gaining appreciation and mortgage pay-down in your move-to unit so you're probably coming out ahead (keeping in mind that if the previous unit goes vacant you're quite a bit in the hole so you need to have a good W2).

If the odor was in the walls and baseboard, I would wash down the walls and baseboards with a product made for eliminating animal odor.

Often I am replacing floors, or painting/pressure washing, and other misc repairs. 

Maybe a wash

I suggest you do that so you don't one day get a surprise water bill because your tenants started a car wash.

BUT, when I asked, they replied.My realtor seemed more confused/concerned than I was.  He

People that live like that are also likely to ignore leaks under the sink or washing machine or toilet that cause damage to the floor and subflooring.

You could go in there with a hose and wash it all down.

Be especially careful charging a tenant for the entire cost of carpet when the carpets are like 10 years oldPicture or pin holes in walls, as long as not excessive Painting the exterior of the homePressure washing unless there are oil stains from their auto Routine maintenance There are many more circumstances that could and will come into play, but lets all work together to come to a resolution.