The least destructive way to check for a leak would be to insert one of those fish cameras into the register (like the ones used in cars to check cylinder condition).

Go look at the property and start negotiating the purchase price with him again once you see the condition. 

She has moved out now and we decided to not deduct any money from her deposit for the cleaning because we don’t know the condition it was in when she first moved in, although she did sign our cleaning agreement.

The conditions vary depending on scenario so you’ll again need guidance from your accountant.

I simply refer them to the condition catalog and provide after photos only as needed.Lastly, don't ever waste your time arguing over deposits on the phone. 

Just explain that costs rise each year and that this is necessary to keep the property in good condition.

Constructed in about 1970, building in OK condition. 

They've since paid voiding the eviction but I expect we'll need to do it again next month. sigh...One piece of advice is to make sure the rent is appropriate for the condition of the unit. ie, if it would rent for $1200 fully renovated, what's it worth in its present condition.

But the conditions surrounding this acquisition were a lot different than the two homes I had purchased in the past. 

There's a huge % of our country which votes to give up more of their privacy and freedom every time they're given a ballot whether or not it's in their best interest because doing so typically has some "feel good" gift wrap so we find ourselves in a tough situation as social media/tech/business/finance/foreign interests collide under these conditions.