Hi @Sammi Liu
Vacancy rates: there is no real data available industry wide for vacancy rates in the rental of Single Family Homes as most of the data we have comes from the Multi-Family market - so properties with 2+ units.
Your most accurate sense of the vacancy rates will come from calling and asking current Property Managers and even then it will be anecdotal and possibly biased by the desire to secure your property rather than accurate data you can use to assess your risk adequately but it gives you a 'feel'.
The best way to get a sense of the vacancy rate of Single Family Homes is to test the market. Place an ad and see what kind of response you get.
Additionally, search for a property for rent in the neighbourhood you are considering at the rental price you would like to command and see how many properties are available currently and how long they have been available. This will help you to take the temperature of the market.
I just did a quick search for you in Sarasota of 3 bed properties for rent in the past 3 months and there were only 3. I know for a fact that the Single Family Rental market here is starved of good SFHs rentals and they go like hot cakes when one comes on the market.
In terms of Property Management - I would agree with the other comments above - finding a good PM is probably necessary unless you want to establish your own team down here which people do do - it just depends on how much time you want to devote to it...