If you are talking smack on the beach and direct view of the Gulf Of Mexico I would think that Fort Myers Beach is one of the most affordable places to own on Florida's Gulf. You can get a condo at $659,000 with 845 SF 2/2 at good looking Cane Palm Beach Development or a $895,000 single home of about 1200 square feet but also smack on the Gulf.You can also opt for smaller SF and get a 1/1 for under $300K at the New Pink Shell ( under 400sf ) or at the renovated the Sanibel View villas next to it on the North of Fort Myers Beach with the lowest price at $269,000.There is also a fractional condo ( 6 weeks ownership at the Neptune with condos starting at $75,000 )- The larger condos smack on the gulf of course are much higher priced.
If you are talking "close to and by the Gulf " you can get a very attractive condo at the Seagrape Condo for just under $300,000 with view of the Bay and 3 mn walk to the beach and you can own a home less then 5 mn walk to the beach in the low $300K
Pine Island and Cape Coral which are South of Fort Myers Beach, also have a terrific amount of choices with condos under S120,000 and about 800-1000 SF close to the Caloosahatchee which falls into the Gulf of Mexico.I saw about 60 condos under $150,000 from 700-1100 square feet and 2/2.
Its all about location of course. It all depends what kind of home or condo/townhouse you are looking for.
Bokeelia in Pine Island offers homes under $130,000 but I believe that for a decent home you ahve to spend about $220,000 for starters ( about Pine Island: http://activerain.com/blogsview/52436/Pine-Island-Where-Hemingway
) and has the Old Florida Charm.
As you can see South West Florida has alot of choices. If you have any questions feel free to write. There is just to much to be able to squeeze it in one small answer.I do know we are very very competitive and of course South West Florida is a glorious place to live.