I presently have 2 R/C Sailboats and am working on a R/C USCG 41' UTB. My first R/C sailboat was an 18" ketch that I scratch-built in 1987, it sailed pretty good, and fast! This was not a racing boat...... more or less it looked like a typical 40' cruising boat (center-cockpit, cut-away full-keel) and even had a dinghy on davits. I think total cost was around $50 +/- I stopped using it when I got my second R/C sailboat (needed the radio and servos for new boat!).
My second boat was a 33" long sloop (Cosmic Wind) that a neighbor of ours gave to me. He had built is from a kit and enjoyed sailing it.... but seemed to enjoy letting others sail the boat while he watched (he had been a casual sailor for many years, had a Town-Class 15 years earlier, and a DS II for a few years after that) He knew that I was getting interested in R/C boats (power and sail) and maybe felt it better to see the boat get used instead of sitting in his basement. I have had a lot of fun with the boat since I got it in 1988, I painted it and have modified the rigging a bit for better sailing. I later used the hull of that boat as a "mold" to construct a larger boat (35") that is strip-planked with balsa wood and then covered inside and out with lightweight fiberglass cloth. I have sailed that boat off and on since 1993, even making my own sails.
All of my boats have used a 2-channel radio for control, I have used mostly a pistol-grip style radio in these boats, using the wheel for steering and a trigger for sail-control. It does take either a strong servo or a "sail-Control" to trim the sails. The biggest problem with R/C sailing is that unlike a "real" boat, there is no "seat-of-the-pants" effect.... in other words, you are sailing the boat from a distance and it does take a bit to get used to. Steering takes a bit to get used to when you are sailing towards shore (in other words, the boat is heading right at you) since you have to remember to turn the wheel (or move the joy-stick) opposite to "normal".
My very first experience sailing a R/C boat was way back in 1977 when there used to be a guy down at Falmouth (Mass) Inner Harbor who rented out models for $0.50 for 15 minutes. It was sure fun! Unfortunately, I tried it late in the day...... and the wind was dying!
That brings up an answer to the becalmed question. You should have some form of "chase boat" when R/C sailing, or sail only in waters where you can easily wade out to retreive your boat. Some larger models, and in fact it is not impossible on even the smallest R/C sailboats, will have a small electric inboard auxiliary (I even have a folding prop, but have not installed a motor yet) as get home power. Radio range is about 1 mile max, but that depends on battery strength. There is a device mostly used in R/C planes, but that should work on boats, that will move the servos to a "default" setting if the radio loses signal, this might be set to let the sails out and put the rudder hard over to keep the boat sailing in a circle, or maybe just come about......? I read a good tip that recommended only extending the transmitter antenna about 3/4 length, then is the model loses signal you can extend the antenna fully and get it back. Definitely you will want to mark your model with your name and address under a hatch or on the deck, "Just in Case"!
I'll see if I can scan a few pics of my boats!