Typically, you have the fitting BEFORE you acquire the bike ...
With the bike in hand, you should check one of the many on-line frame fitting guides -- e.g.,
The Colorado Cyclist :: Bicycle Parts and Accessories (this will probably get you 95%-to-99% of where a "professional" fitter will get you).
What vintage is the bike/frame?
What is the length of the top tube (c-c) & seat tube (c-c)?
What is the length of the stem?
Does the bike have 700c or 27" wheels?
AND, how tall are you?
I recommend you save the $50 on the fitting & spend it on a copy of
ZINN AND THE ART OF ROAD BIKE MAINTENANCE from your local Barnes & Noble, Amazon, eBay, etc. (OR, you can probably borrow from your public library, first).