its as easy or hard as you want to make it, depending what style you are after – your best bet is to type project or chop into ebay and find something unfinished. Theres loads about, from frames to nearly complete bikes. Other option is to buy a bike, junk most of it and fit the bits you want on it – where abouts are you? there may be someone nearby who can help….
EDIT : Welcome to the forum BTW…
I slept with faith and found a corpse in my arms on awakening; I drank and danced all night with doubt and found her a virgin in the morning.
Aleister Crowley (1875 – 1947)
Blackboard paint – Covers a multitude of sins!