I highly recommend the Tides. I actually lived there this past summer while I was renovating my new home and had a great time. The building was recently renovated with new balconies and the amenities are superb. The staff is wonderful and the beach and pool area are incredible. Definitely a great rental property. As an investment, you want to get into something that is relatively new or has recently been renovated so that you don't have any unpleasant surprises. A rental on the beach is prime real estate any way you see it.
I know several people at the Tides and know the building inside out. If you're interested in seeing a few units, please let me know. The shoulder season is a good time to buy ( Right after Easter) because soon the snowbirds head back North and rentals slow down before the summer, so owners tend to become more "motivated" during this time.
A few other good rentals - although not on the beach, but in Aventura, are the Yacht Club and Village by the Bay. Great ROI and high rents because they're in Aventura. More so as seasonal. The downside is no beach, .... but you have the mall. The Marco Polo in Aventura offers a hotel rental program. You buy your unit, put it in the hotel rental program which splits the revenue with you and when you come, you simply make a reservation and stay in your unit. Each property has it's pluses and minuses... it really depends what you want and where you want to stay when you come for your vacation.
Many owners either rent through Real estate agents or through sites like homeaway.com or VRBO.com. these are excellent seasonal rental sites. I know of a few others that I can share with you. That also happens to be my expertise since my background is in the hotel and property management business... short term seasonal rentals and vacation homes are my thing.
Give me a call and I can show you a few of these units as well as help you rent them out on a seasonal basis. 305-733-8782