How to find where water is getting into interior on passenger side?

I had to see a mechanic to find the source of the check engine light because it wouldn’t pass inspection unless the light was out. He said I had four codes. Also, the blower motor was burnt out.

He replaced a few components in the interior of the engine, installed a new battery and a new battery brace. He put in a new blower motor behind the dashboard compartment and a new AC filter.

He charged me $410 in labor which seems way too much.

Since the repairs, I’ve had water entering my vehicle’s interior on the passenger side. The mechanic claims he knows nothing about it. The water sloshes to the back passenger side.

Where should I be looking to find where water is getting into interior on passenger side?