Or be simple and use rehydrated dry yeast and save yourself money and headaches. I quit wasting time on liquid yeast awhile back. Not saying its not good but why work harder instead of smarter, meaning making starters, stirplates,spending 2 or 3X the money, making that wheel roll a little better, etc?? I have superb results with the properly pitched amounts of dry yeast.
Once you get more into brewing do what you want but for those starting out dry yeast is the ONLY way to go.