If your buying the bow new it should be set up as you want it at purchase.
Most bows have a 10# range
Say 50-60# bow or 60-70# bow ,
There are some bows with a wider range.
Once you have the bow, and know # its set at you can adjust it yourself, and just have a shop check the poundage on occassion.
My shop/range doesn't charge to check the poundage but they will charge $5-$10 to change the poundage.