The MLS data sheet has a data fields to describe the amount of the HOA dues and the period I/e/ monthly quarterly or yearly. If the property is listed the MLS data sheet is supposed to have that information.
After it has been listed the seller signs a homeowner association questionnaire to the HOA management company. On the questionnaire the HOA management company is asked your question along with a dozen other questions regarding parking, storage, age restrictions, special assessments, insurance coverage, rules, etc etc. The questionnaire also requests copies of the by-laws, budget, rules, articles of incorporation, copies of the minutes, etc etc.
If the listing is new when you make your offer the HOA may not have returned the questionnaire yet. Your buyers agent will be sure to request one.
Usually the HOA management will charge a small fee to cover the clerical expense of providing the documents and making copies. When you are dealing with a short seller or a bank, the HOA doc fee will probably be an upfront buyer paid expense.