Using "is it available" to start a dialogue is perfectly fine.
I dont see an issue to respond "yes it is" to every one of those unless you are being spammed.
However whats worse is when you get ghosted after concluding the deal and the buyer is on his way to view but never pitches or when they "quickly going to draw cash at the ATM" but never returns.
Just saying its completely fine to test ride, inspect, ask questions etc and if you decide you dont want the product at the very end then just say so. Its not like im forcing you into marriage after youve taken my V card