I have a pretty air tight lease but there is only so much a lease can do...one can put down on the lease don't put the following five thousand things into the disposer and the following three thousand things into the toilet, but no one reads it and having someone with common sense is important.My personal experiences with roommates who don't know each other have been not so pleasant. 

Some may want two toilets, or his/hers bathrooms, or a shower, or laundry.

Even if I'm on the toilet, I answer the phone.

Removing trim, carpet, doors and toilet is about the easiest thing you can do even if you’ve never done it before.

Water heaters, softeners, toilet tanks, and anything else in the house that holds water. 2.

You never want to walk into a bathroom and the first thing you see is a toilet or a shower.

If the drains/toilets are running fine when they move in then its the tenants responsibility to keep them that way.

If these tenants had been living there for years, were you at all concerned about squatting or destruction of property?

Another time, the toilet got replaced & in so doing, the workers damaged the surrounding floor tiles and were not able to find matching tiles.

She would be squatting your house.