@Mike-and-Marcia0 Airbnb does not offer a method of building a demographic-selective discount (e.g. military, senior citizen, government, etc) into the booking process, so they're really not a thing. If Airbnb wanted to extend special discounts as a company (out of their pocket, rather than the hosts') they would do so. But you can take comfort in knowing that you are by no means expected to have your own discount system.
And I really don't recommend taking these requests seriously - guests who want certain types of discounts should stick to chain hotels that have a system built for them. If you get an inquiry from a guest that you'd like to offer a special discount for your own reasons, you can respond with a Special Offer of your choice. But I'd be wary of guests who ask for a discount in the booking process; you're not a corporate hotel chain, so what these guests are actually asking is that you take a pay cut for your own hard work. These guests are significantly likelier to undervalue your hospitality and "reward" you with an underwhelming review.
If you respond that Airbnb doesn't have a military discount system and the guests still decide that they're happy to book your place at its regular price, everything is OK. If you feel inclined to offer something special for members of the armed forces you are of course free to come up with a nice uniquely Nashville gift to offer upon arrival.