@Gino Barbaro  I suppose someone could run into the loan to own snakes out there.. but the good reputable HML do NOT want to own the asset ever ..

@Aaron PhillipsPlease accept my sympathies on this, the first time in this business that a snake swallowed up your time and toil only to slither out of a verbal agreement on you.I can promise you that it won't be the last time.As far as legal options go, you have none worth pursuing.If you should take it into your head that extra-legal options are the way to go...my advice is to wait six months and see how you feel about it then.

I even thought of breaking the lease because the lease say no pets and theirs a snake in the basement.Should I see a lawyer about this?

I would avoid kicking in cash to a deal until you get a feel for things, there are some snakes in the grass. 

@Billy San Roman snake oil salesmen 

He reminded me of a snake when I first met him, but the lure of a quick and lucrative sale made me over-rule my gut.

Might even try running a snake down it.

Since one unit is flushing fine and no back up and the other unit is backing up into the tub it indicates that the clog is localized at that unit and should not be far beyond the actual toilet drain seeing that the other unit is not affected.So if this is the case, that means you probably have no issues with tree roots or a collapsed line but rather some type of substance that is clogging up the immediate drain.Was an auger (snake) ran through the line?

When the professional plumber came in to fix the leak they mentioned they had to use a 30 ft snake to unclog the pipes.I went to file a claim with my insurance and they said it is not covered because the issue did not happen with the pipes inside my specific unit.

I know way too many people who have been bit by this snake.