Is this what you are saying;
1. Your tenant is a man who occupies this unit with his family.
2. His mother does not live there
3. A few months ago he complained about a bad sewer smell in his unit
4. The smell was so bad that his kid had to change clothes in school not in unit
5. When he first complained you went to investigate & couldn't smell any strong sewer odor
6. When you went a few months ago you said it was OK for his friend to check it out & you would pay him if he fixed it.
7. Now a few months after his mother who does not live there is complaining about the smell being so bad that her son should be able to break lease & get a full refund.
8. Now the son said he wants to leave & get a full refund.
9. You are going there tomorrow to check things out for yourself. Then depending upon what you find you will have a plumber or a drain cleaner fix it.
Did he ever have his friend check things out a few months ago? If yes what did they find? What did they do & did you pay the friend?
When you go there I suggest that you do this:
1. Go when the tenant can be there to explain when & where he smells the odor.
2. Bring someone with you to witness what you do & to smell for the odor.
3. Shine a black light everywhere he says there is an odor especially around the toilets. In addition to the bathroom do this in every room especially where there is carpet of wood flooring. This will show if someone has been peeing on the floors or walls.
4. Pour some bleach & water into all of the drains, sinks, tubs, laundry & floor drains
5. Ask the tenant why if the sewer smell is so bad he waited a few more months before saying it was so bad he had to move.
Unless you & your witness can smell the sewer odor or see urine stains with the black light, I'm guessing that the tenant just wants to leave & is scamming you. If you do smell the sewer odor and / or the black light shows signs of urine let us know & we can get you suggestions on how to handle it.
--96.237.xx.xx