There are many municipal parking lots in Miami Beach, the largest being at 16th and Collins (entrance is off 16th street). Municipal parking charges start at just $1 per hour and this 16th Street lot charges just $16 for 24 hrs. The lot at 5th & Alton Garage is free for the first 2 hours, then costs approximately $1 per hour up to $20 for 24hrs. Handicap accessible parking is free "at at all on-street meters, surface lots and garages" run by the city.
Metered street parking is either $1 or $1.75 per hour depending on location with maximum stay listed on the meter. There are smaller lots right off the ocean, but can fill up quickly. The City of Miami’s website has lots of good information on municipal parking for South Beach here. You can use that list with the map in the pictures below to know where the lots are, along with the total number of parking spaces at each. If you are looking for longer term parking in Miami, you can read my other article here.