Bicycles stop better with front brakes (but don’t hit the front brake too hard or you will flip over). This generally requires a hand-operated brake on the front wheel.
I was amazed at the improvement in gears and hand brakes in the newer bikes over my 15 year old bike. Definitely, go for a test drive on several bikes.
I also bought my first bike in many years and went with this one:
http://www.rei.com/product/851142/electra-townie-7d-step-through-womens-bike-2015
Love it! (My kid took a look at the orange and white color scheme and immediately dubbed it “The Creamcycle”.
I agree with those who suggested doing test drives at a reputable bicycle shop. Love the one that I got; very comfortable ride. I also thought about doing coaster brakes but was convinced by the bike shop owners that hand brakes and variable speed (in this case 7 speed) would be better (they were right.)
I wouldn’t invest a ton of money as climate is going to play havoc with rust etc if it is just a beach house bike. If you know someone who is a bit mechanical, bikesdirect.com is a great choice. Online bikes need an eye cast over them by someone who understands bikes though. Gears, get them. Real brakes, get them, A proper rack for shopping would be a necessity so look at the hauling bikes, but they are $$.
When we first moved to Portland, I bought a Swobo city commuter with coaster brakes and an 8-speed hub (think single twist shifter in the handlebars). Aluminum frame. It was fun to ride in most of Portland but impossible in the hilly area we moved to after the first year. I found coaster brakes just fine to use–I’m not sure why anyone thinks handbrakes are easier or safer. (I’d argue that coaster brakes are safer because you can use your hand to signal while you’re braking.)
Less expensive bikes these days often have aluminum frames instead of steel, so rust should not be a problem. Keeping the chain properly lubricated does make a difference. Rinsing the bike occasionally to remove salt would be a good idea. Keeping sand out of the chain can be an issue at the beach but it’s fairly simple to clean a chain.
I was surprised to see people riding fat tire bikes in the snow this winter. I wonder if they would also be good at the beach?
http://www.seattletimes.com/life/outdoors/fat-bikes-make-tracks-on-snow-and-sand-and-mud-and/
My recommendation would be to acquire the cheapest bike you can find as a first step. There ought to be a number of people who ended up buying a bike and being sweet talked by a bike shop owner in spending way more than warranted. That first bike will ensure that you even like it enough to keep using it (and caring for it) in the following summer seasons. You might also discover that your favorite bike is different from others.
After settling on the style, the “cheap” starter could be unloaded to the next new bike fan with just a small loss. Once you are convinced, time will come to splurge and buy better equipment. There are two things I have spent small fortunes on: snowboarding and biking and the biggest mistake I made was to buy “middle of the road” equipment that was too expensive for it was and too cheap to be truly enjoyable.
Fat tire bikes-- really fat tires, 4" or 5" wide tires, not the cruiser tires-- are way fun in the snow and on the beach. But a fat bike (a bike with fat tires) is more of an enthusiast’s bike than a casual beach bike.
to the OP you might enjoy www.bikeforums.net
My daughter goes to college in a beach town (flat). She wanted a bike so we went to a bike store and they were hundreds of dollars for a cruiser. The owner was nice and told us not to waste the money, the that bike WOULD be stolen. With a lock, with storage, it would be stolen. She got one at Target and while she was gone for Christmas break someone damaged her tire beyond repair.
Other daughter goes to a different college where they have a fleet of bikes for rent by the semester. Coaster bikes. She didn’t find she needed one but some kids ride them all year, with snow, rain, wind.
We ride mostly on paved bike trails. After years of riding a hand me down mountain bike from one of the kids, I decided it was high time I bought another bike. I chose an Electra townie with 3 gears and I am loving it. Super simple and the upright riding position is comfortable. Plus it is so darn cute!
The bike our kids used in college were $7 beater bikes–functional but ugly. They never had theft issues with more attractive bikes nearby.
We bought nicer bikes for home and they had lost interest long before S’s bike was stolen.
We have all sorts of bikes: road bikes, racing bikes, touring, mountain bikes but no cruisers. D thought she wanted a cruiser bike a couple of years ago. We went to the local bike shop where she test rode several models including cruisers. She said it was too heavy and too slow. She ended up with a very nice hybrid “city” bike that sat very upright. It has a gazillion (24? 27?) gears but she doesn’t use them all. You may end up needing gears even on flat land, because there’s with the wind and against the wind. Against the wind can feel a lot like uphill.
I second or third the suggestion of going to a good bike shop with a good selection and just start riding bikes. Make sure the bike fits you. And of course, get the helmet.