Making your own could be a great idea. But if you do, make it look good, and make it last in the weather.
Here is how I have created a beautiful natural wood A-board sign for a massage company with professional lettering and a chalkboard on it.
1. Buy good hardwood plywood. At least 1/2 inch thick, but 3/4 would last longer, and the heavier wood will not blow over as easy.
2. Cut it into an attractive shape - two identical sides.
3. Coat this beautiful wood with exterior Varathane (a plastic based wood coating). The Varathane coating will give dry clear, leaving the beautiful wood, and protecting it from the rain and sun for years.
3. Bind the two pieces at the top with one long hinge, or two smaller ones. USE STAINLESS STEEL hinges, so they do not rust and look bad after a little bit of rain.
4. Screw some big stainless steel wood screws into the bottom edge that the sign sits on (screw them all the way in so just their heads stick out). One for each corner. Drill holes first so you don't split the wood. Your sign will sit on these screw heads. That will keep the wood off the wet ground and make your sign last much longer.
5. Add a chain down low inside the sign between the two sides to keep it from spreading too far (as mentioned above).
6. Figure out what words and numbers you want on it, and go to a sign maker (take your sign), and have them create the words you want on the sign in Vinyl lettering. This generally is very inexpensive. It is the same type of lettering that goes on windows. It will look great on the wood. (Or you could paint your own if you make it look professional).
7. You can also purchase black board paint at a hardware store. Get some masking tape, carefully mask off the area you want to have a chalkboard on, and then paint on the black chalkboard stuff. When it dries you can use the soft color chalks on it (not the hard white stuff) to create changing messages and specials.
Or, you could just pay a sign maker to do all of that for you (or barter for massage!).