This is one thing most people have been asking for some time now, since it is obvious that there is a bigger and bigger demand for instruments, like used guitars for instance, online. It is completely understandable why people would question the safety of doing this online, since they are handing over real money and instruments to complete strangers
Well, to put it simply, the safety aspect depends on the online platform the buyers or sellers use. After all, they cannot expect to get a reliable deal from a shady vendor on the streets, so they should not expect the same from a random online platform they just found online.
They should only use an online platform that is reputable, has decent reviews, and offers quality safeguards to ensure people do not get scammed. Also, the platform must allow them to easily communicate with potential sellers/buyers so that they can easily finish their business. Sounds exactly like the reliable, quality service found at http://www.musicgoroundaurora.com/.
If people do this, there should be no problem with the security aspect, as all their data will be safe. Of course, they should also never work with platforms or people who ask them for personal bank or credit card details to improve their safety online.