Hello ,
I want to know that if I buy a page rank domain which is recently expired, for how long will the domain maintain its page rank if I does not add content/website to it?

And if I add content/website which is not relevant to the domain, then shall I loose the page rank or still maintain?

Even if I loose the page rank, then it will still take 3-4 months until google next PR update. Am I right?

Please elaborate and write your experience,knowledge here