About bass guitar

Hi, i want to ask what bass guitar should i choose? I would play rock, blues if that matters. I can spend about 450euros and i'm not a total begginer of playing bass. One of my friend sells bass right now, it's ibanez sr505. I played it yesterday, it sounds really good but there's a problem with metal. The guitar was in a box few years and nobody has used it, there aren't any sratches on the wood but the metal looks like rusted. And that's not rust honestly, i don't even know how to discribe those spots, but it doesn't look nice. I want that bass but how can i clean those spots? And what if it doesn't clean? I don't want bad looking guitar for 600dollars. But if buying guitar from the internet (there isn't a big variety of guitars in my country) I'm afraid that my guitar will be damaged or they will count more money than i could spend (i have heard lots of similar problems). So i'm thinking what to do and i want your advice: choose that ibanez and risk to clean it or risk to buy new guitar from internet? And another questions: if i should choose to buy ibanez, how can i clean it (what remover or something like that should i use) and if i choose to buy new guitar what exactly guitar should i choose (i have given some aspects in the begining of my message)?