hi there - i had a bike i liked a lot a few years ago (an iro mark v) but it was stolen and i haven't had a bike since. i finally have enough money together (~$450) where i think i can buy something that won't make me too bummed out about the last bike i had.
so with that said, i don't know very much about bikes. i wouldn't mind learning more, but while looking on craigslist i've quickly found that there were a lot of terms i didn't really understand. i spent a few days doing research (so i really still know nothing) but i now know a little bit about different frame materials (thanks to metallurgy for cyclists by scot nichol) and more importantly i know that a single number won't be representative on how strong the frame is. but for every other part of the bike which isn't the frame, i have very little knowledge about. for instance the bottom bracket or crankset. with many older bikes it seems lucky if the owner knows the frame size, let alone its composition, reputation of the manufacturer, or the proper identification of most of its components. i'm sure this is something that just comes from seeing a lot of bikes and learning about each part's functionality and design, but i'm clearly not someone who has.
with that said, i've decided on trying to find a used bike with a decent frame that i can improve the components on later as i learn more. but knowing how little i know, is there anything that i can do while looking at bikes to figure out if it has any defects or is decent? should i stick to a name-brand bike where i can research the frame myself, like a steamroller/pista/iro/etc? is it usually assumed that if the components aren't named, that they are stock and i just need to find its year?
i considered for a while buying a new cheap bike (like a kilo tt) just so that i can start riding and then replace parts as i learn but i think i don't mind going a slightly more difficult route if it means i learn more sooner, conserve energy/raw material, and possibly get a better bike for the same price.
so with all of that said, any recommendations? i just moved to new york city and fortunately there are a lot of bikes posted on craigslist and a few lbs that seem nice/promising. i'm also willing to change my mind on any of this if there's a compelling enough reason. it's just difficult to look at thirty japanese frames from the 80's and know if any of them are decent (most of them don't have badges/markings that i can make out in the pictures).
tl;dr: please no kilo tt / how do you know if a 'custom butted frame' is well-engineered?