An HOA must follow strict guidelines which are based upon both state law and the by-laws established by the association. A property manager may not increase fees on their own.
Generally, an board committee, working with the property manager, will develop a budget which is then brought before the board for a vote in public session. Community members are invited to sit in.
If you are looking at fees at a mobile home park, where the land is owned by an individual or a business entity, they may generally raise rates so long as they are in conformance with the rental agreement you have signed. In regard to manufactured homes, they depreciate in the same manner as an automobile.