Recently I needed a beam saw to cut nine saw cut grooves 4 ½” deep totaling 5 ¾” wide down the top side of a 200” long beam, so that we could then chisel out the middle of this beam to create a pocket to hide a glue lam beam. I went to Home Depot and rented a Makita 16 5/16” beam saw for $40 a day. When I returned the saw the next day, by the way it worked great to do the job intended; I told them if they ever wanted to sell it, I’d buy it. They said they sell all the tools they rent. And that this beam saw was currently valued at $249.50 (the computer automatically de-values the saw each time it’s rented) and it was available for sale. tool crib sells this saw for $599. This rental saw had only been rented 6 times since new over 2 ½ years. I got it and it works great.
You could try going to your local Home Depot store and see if they have one available for sale from their tool rental section, you might find a good deal there, also. Good luck, Jim

Whatever you do, have fun doing it!