Is it good to use?

[Bogertophis]

...
First the main question: the enclosure. It's a 10-gallon glass old fish tank that someone gave me when they learned I wanted a snake. I've cleaned it extensively with a combination of vinegar and Dawn dish soap, after which I rinsed it like 4 times to make sure there's no residue and then rinsed it again for measure. It literally smells like nothing. However, I can't remember where I heard it but at one point someone said that even no matter how clean it is I should never use a tank that had fish in it. So that's my question, should I get another tank or is this well enough now that it's as clean as I can make it? ....

I've never heard that specifically about not re-using a fish tank, but ANY used tank should be thoroughly disinfected before using. I'd use some bleach for that first,
let it sit & soak a while, making sure the bleach hits every inch, inside & out. Rinse well, no bleach smell can remain. I'd also use a second disinfectant (either F10
or chlorhexidine) properly diluted- to wipe it out again. (& either one is good for routine cleaning thereafter) Dish soap is great for removing dirt, but does nothing
to disinfect. Vinegar is a mild disinfectant, not enough for a used cage. It's also great for routinely cleaning water bowls (removes hard water deposits).