It is common for there to be plumbing problems when the pipes have sat unused for so long. Crap literally dries in the lines & that is likely what is causing your clogs. The owner is the one that neglected their house they are the ones that need to pay for this.
You do not say what state you are in but repair & deduct is legal in many states. You need to send them a certified letter stating the needed repair, they then have X # of days to fix it depending on state. If they still do not fix it then you can have it fixed & take ONLY that amount off the next month rent. Make sure to put this intention in the letter & give a copy of the receipt with the rent.
You may or may not have caused the problem. Get a plumber in there and he will determine what the problem is then a decision can be made.
You don't own it, it's not your concern. Call codes.
If by sewage problems you mean slow or clogged drains, and you are the only users, then it's your responsibility. If there are sewage back ups below the structure or non functioning pumps and equipment, it is there responsibility. It would be in their best interest to take any preventive measures to avoid water damage to yours or their property and you may have to suggest that.
I've just moved into a home and I am renting it. I have only been here one month and I am having sewage problems. The landlord said it was my responsiblility. No one has not lived here since November of last year. The landlord said we caused the problem in one month but we think otherwise.
