I don't understand "there is/isn't no" and "is/isn't there" kind of phrases

A friend asked me if I thought this phrase was correct:

"It seems there isn't a free cam, is there?"

I replied I think it should be:

"It looks like there isn't a free cam, isn't there?"

He objected that the second "isn't" should not be negative, like this:

"It looks like there isn't a free cam, is there?"

I thought "oh yeah, that's right" and said that maybe this costruction was better:

"There is no free cam, isn't there?"

Should it be

"There is no free cam, is there?"

instead? I thought I knew this but I'm doubting it now.

Solution 1:

Each of these sentences -

"It looks like there isn't a free cam, is there?"

and

"There is no free cam, is there?" are grammatically correct.

You don't follow one negation with another. What you are trying to do here is make a statement and then try to look for someone to negate that statement. Hence the single negation policy.