My garage drain is draining very slowly and I think that it is clogged with tree roots.  

The sole purpose of designating a animal as ESA is to get around regulations that prevent pets to be taken into certain areas.

I'm trying to prevent a problem before it happens, and was looking for a more technical answer.Thanks!

I usually break it down into 5 pillars of asset protection (though in reality there are many more...)1st pillar is avoiding unnecessary and risky activities (don't drink and drive, insurance generally won’t cover your poor decisions) and take good care of your investments - these simple steps will help you prevent lawsuits before they even occur.2nd pillar is a good insurance policy as that cover the majority of your exposure.

And is there a way to prevent it, or to see if the tenant was a problem prior to the purchase of the property? 

I thought about having the PM putting language in the lease agreement for the tenant to not let food go down the sink , tenant would be responsible for any kitchen sink clogs going forward, and perhaps require use of a sink strainer but given there was glass found during the 2nd repair, I am not sure how careful or compliant the tenant would be anyway.In addition.. let's say there is a clog in the kitchen sink with no GD, plumber takes care of it,  is there any concern about the impact to piping long term should residual food waste be allowed to accumulate in the pipes? 

@Kyle Gilbert I agree with the group here...in difficult situations or with combative tenants it may make sense to issue LOI or even a contract with a contingency...so, get in the units you can, get the property secured with a LOI/contract, and then leverage the seller to see every inch of the property before you can remove the contingency and close the deal...It's amazing the lengths some tenants will go to in order to prevent a deal from happening out of fear of the unknown...it's good to have leverage on the seller to assist with getting in the units if they want to sell the property.

It may even prevent them from feeling entitled, as many kids now days seem to feel.

You'll probably also need a back-flow preventer installed.All that being said, If you do replumb interior, pull permits, use PEX and put that in your house description when you sell. 

I messaged cozy support, and they replied below which seems very bad to landlords.Reply from customer service: unfortunately, when it comes to payments being disputed, Cozy does not have the ability to prevent it from happening.