I sold my short arm setup to a lady in the next province. I think she drove more than 5 hours. We negotiated price over the phone, and I showed her and her 2 friends that she brought to help load and keep her company how to use it. DH wasn't here that day because of the time she was going to arrive, but in most cases, I would usually recommend that someone else be there with you.
I sell quite a few machines on Kijiji (our version of CL. We have CL, but for some reason it's just dead.)
I often break the rule of not having someone else home, but I try to time the appointments for when DH will arrive home soon from work, usually during the appointment.
I also "prequalify" people when I talk to them on the phone. Often you can tell by talking to them what sort of person you're dealing with then decide if you want "backup" when they arrive. You can also build a little rapport with them on the phone and in person which tends to make it easier to get your asking price.
I always give them everything I know or have for the machine - i.e. things I've printed out, etc. I offer way more (in knowledge) than I hinted at in the ad and they usually leave feeling like they got their money's worth and more even though I stuck to my price. I've even been "tipped" for the info I've volunteered. LOL!
At the end of the day, if you can explain why your price is the way it is, and it's based on logic - "Well it was my mom's..." doesn't work but "I'm asking $125 for the serger, it's fully serviced and ready to go which costs $90 at a shop and it comes with all these accessories that didn't come with it originally, basically the machine and accessories are $35" is usually no problem at all.
If the buyer still doesn't "get it" that you put money out to buy it, did the upkeep on it to keep it in tip top shape for them, are sharing your expertise with them, etc then they're not the buyer for that item. You still have the right to escort them to the door.