I got a plumber out again 2 days later to unclog the sink again, he found cooking grease was causing the blockage. 

Tenant maintenance can put the landlord into a bind where the tenant expects (and can demand in court) rent credits for work performed and you have no idea of the appropriate solution/code adherence.My lease specifically states that the plumbing is in working order without any blockage and if it does occur, it's the tenants responsibility to call the plumber.Even with 6 units, I don't get multiple  calls per month - - heck, maybe 4 calls all year.

The rooter guy hit a blockage that he was eventually able to push through and then scoped the sewer.  

You will more than likely need to get someone to snake the drainage line for blockage.

My doctor told me that 99% blockage due mostly to stress almost killed me without warning.

A neighbor three houses down called another plumber that did snake the line and he cleared a blockage as it tied into the city line but said that there is another obstruction going the other direction that they are putting a camera on tomorrow.  

Finally, they pulled the toilet to see if the blockage was in toilet or the sewer line.When they called that Monday about the issue, they said something was – I quote – “in there.”

Sewer blockage is home owners problem.

We has him snake the line and he said there was no blockage and we should call the county.

The other line had a blockage, so he was unable to see very far.