Local pickup for speakers - should I let the buyer in the house or use the the garage?

I would demo the speakers in the garage using my oldest cheapest amp and sources, just good enough to show that the speakers work.  I don't need to make them sound good, especially given garage acoustics and the mediocre upstream equipment -- not sounding great would be understandable.  Presumably, the buyer has already decided he wants these, so I'm not trying to give a sales demo here, just show that they're not broken.

I’ve always let folks in and been invited in to verify the equipment is working before a deal. If you feel uneasy have a friend over too.

Have another person present, and let him in.

I would talk on the phone. Learn about their interests and background in audio. Any legit will be happy to talk and be concerned about what they are buying. If they are cagey and want to get off the phone... I would not do business with them. 

I'm pretty much alone in this city. I wouldn't be able to get anyone to be here that I know.