When I was inspecting the property right before closing, I flushed one of the toilets and it flushed REALLY slowly so I'm sure I'll need that very soon. 

Every time it flushes, you can hear loud noises in the pipes as the water moves through.

No big deal .I have 2 kids that dont turn off lights , tv's or flush the toilet .

Cheap toilets don't flush well and mechanically break under wear.

Toilets can leak around the seal, showerpans leak, and washer drains have leaky joints, and water leaking from an upper floor can travel along pipes and drip down to the house sill or into the soil.Have someone flush toilets and run sinks while you are in the basement to listen for tell-tale drips. 

Draining, flushing and even replacing the anode rod all are items you should do.

Construction workers must have flushed the paper towels down the toilet during the remodel.While Jim was still there, I brought up to him what Kay had told me, and if they were aware that there had been sewer issues with this house before.

I flushed the toilet multiple times, ran the water in the sink and tub, and everything seems dry, so I assumed it was an old leak that had been repaired. 

And even if you don't, its my opinion that you file the complaint anyway to flush out folks like this.

(example is toilet was clogging and seemed to me that they were not holding the flusher down long enough to get enough water to fill up the bowl and flush.