We decided to give them all their rent/security deposit back to get them out right away, but of course, they left a parting gift of a dirty house (they had 4 kids), a washcloth flushed down the toilet causing a major clog for the plumber to clear out, and a week's worth of water/sewer/electric/gas bills.

Which also teeters on what a wholesaler does there are asset and trade concerns that can flush out if a deal is good or bad as well.Asset pools in Detroit were probably one of the more common geographic pools in the public domain.

When it comes to toilets if the tenant or the tenants' kids are flushing things that should not be flushed then yes, they are going to pay.

We generally do 2 flushes to make help make sure the line is cleared. 

I would have your worker in the crawl space under the bathroom and flush the toilet and run the sink and tub to check for leaks before installing a sump pump.

I thought it was strange that you said there are some properties around Flushing, NY for around $10k...

Dumping coffee grounds or grease down the drain, using powdered detergents (both laundry and dish) and flushing feminine hygiene products are killer on your septic system.  

But if the lines weren't thoroughly flushed there could still be water in them.

Unless the appraisal is done by someone who specializes in parks (which is rarely the case) you might as well shred it and flush it down the toilet.

It definitely pays for the time to do this.Retrofit toilets with different valve fillers that reduce the flow by 1.5 gallons per flush.