First of all – and you likely know this already -- Minoxidil is not approved for hair loss other than on the scalp. There may be serious health risks associated with using it other than as indicated on the label. Secondly, there is little-to-no evidence that it works for increasing body or beard hair. From what I have read, many of the "success" stories of this use have come from men in their early 20s or younger, who may have been on the point of growing new hair naturally.
Now, knowing all of that, I did try applying it to my chest (and frequently to my beard ; I have a small area that doesn't want to grow hair) "just to see" if it did anything. I used it consistently for about two months, then for another month after a break (in my mid-30s). To be completely honest -- it may have done something. I have a little bit the impression that I have more visible hairs on the edges of my chest than I did before. However, I did not take before and after pictures, so it is very hard to tell for certain. IF it did make a difference, however, it was a very slight one. I am not very hairy to begin with, so any differences would be easy to see, and I am still not certain there were any at all. If you cannot grow a thick beard and are hoping to fill it out, you will likely be disappointed.
Now, it is your life. If you want to experiment, it is your decision. However, please be aware that it is potentially dangerous (always consider the risks), and if you choose to try it anyway, I recommend not having any expectations at the beginning, so you are not disappointed if nothing happens.