I found more abuses there, where required notices are not given at all, yet the bank claims they sent it, and since they are not required to be accomplished by registered mail or public notice, no proof is required.

This isn't something I really like b/c I can totally see tenants abusing this so I wanted to know how do you handle this?

I don't enforce the late fee provision of our lease typically...until I get to an eviction, which is rare....or there is a pattern of abuse with it.  

I am super proud of that and have an infinite amount of respect for him, but I also saw that money really stresses people out when abused and not respected.

This is covered in our forum rules: H - No Abusive Behavior.

Granted my house isnt an A house or an A neighborhood but its close to UWT, on a bus line, and walkable to 6th ave nightlife which seems like about the market youre talking about going into.

But I do not believe abusing my tenants by taking advantage of them in this way. 

Never take abuse from anyone.

They have been good tenants overall but their use/abuse of the plumbing upstairs is getting expensive.  

I suspect that it is 1 or 2 tenants in particular that have toilets running constantly and/or are just abusing the fact that they don't have to pay for water.