For the first time I am buying an old domain which is PR4. Since, I haven't dealt with buying an existing high PR domain before, i wanted to know how to make sure that the domain is genuine and the PR wouldn't drop right after I buy it? And any other extra info you might want to advise me with. I could really use your help here. Thanks.
Continue to build links on it and try and ensure that the links pointing to the domain at the time of purchase do not cease to exist.
While Buying Pagerank Domain,always make sure that it has atleast PR5 backlink to it and make sure backlink is natural and not from seller network of sites. Check info:domain name in google with www and without www to see whether domain has fake or real PR(if the domain name appears below,then PR is real and if other domain name appears,PR is fake). You can use SEOspyglass,Seoquake to check Pagerank backlinks of any domain.If you buy any domain in Pagerank,make sure it has one highest number backlink to domain you buy to avoid Pagerank drop. I hope my tips are useful to you.Good Luck