A way to tell how much is the apartment cap in a specific area

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Hi everyone, i'm about to buy an apartment in Florida - Jacksonville, FL 32254.

How can i tell if the price that that the seller wants me to pay, is according to the apartments cap in this area? 

Do i have to find an appraiser and send him to the apartment or there is another way to find out how much the price of the apartments in this specific area ?