The advice above is really great!
A trio is a good way to start and cost-effective. You definitely want to know the lines, find out if they are in different pens or mixed together, etc. Most people have different pens and can give you birds from each one so they will be totally unrelated...
Most of the well-to-do farms charge well $100+ per chick straight-run. Oh, and don't forget the minimum requirement, its ridiculous! I just got criticized/lectured in the buy/sell/trade forum the other day for stating I would rather buy several hatching eggs for $100 than just one chick.