First off
Welcome to BansheeHQ
In my opinion you have two options.
A- Find one as cheap as possible because you're going to change about everything.
B - Find a built bike and save a few dollars.
Either way you're going to learn to build / maintain your bike.
I built my current drag bike and really enjoyed the entire process.
Just keep in mind that if you build your going to spend at least $4,000 -$5,000 and it won't end there.
Once again Welcome
Troy