A few issues I see here.
1) In many states, only a licensed authorized wholesaler or retailer can sell certain types of medical equipment. So if that's not you, there is the high probability of legal issues that could cross the line of being criminal. For example, the selling of x-ray equipment must be done by either an authorized retailer/whole seller, or an individual who has been licensed to use that x-ray equipment and their license is still valid. A medical professional would probably be licensed to possess and use x-ray equipment. Heck, in my state you can't even sell it to or give it away to a recycler for scrap if you're not licensed for it in some way. So you should seek legal advice from at least your county on this.
2) Sales tax is a local issue, and has nothing to do with income tax. Most states and even lower level's of government within a state impose a sales tax on the sale of physical product. So you'd have to check will all potential taxing authorities to see if a sales tax is applicable here.
3) For most outdated equipment, and especially x-ray equipment, if it's not digital nobody will buy it. But as mentioned above, selling it for scrap isn't like taking your old washer/dryer to the scrap dealer and dropping it off. There can be lots of paperwork involved just to throw it away.
The reasons I point out the above is because my wife works for a dentist, and they had to go through "a lot" of paperwork to get rid of the old analog x-ray equipment, as well as the old analog dental chairs and other medical items used in the dental profession.
he just wants to get rid of it since its just racking up storage costs so he offered me the opportunity.
It honestly sounds to me like you're being taken advantage of, because of your lack of knowledge on the transfer of ownership of medical equipment. I find it difficult to accept that he would "give" you what is potentially thousands (if not tens of thousands) of dollars of medical equipment with no strings attached; even if it is over 4 years old. Were I in your shoes, I'd give the storage locker key back with a "thanks, but no thanks" and walk away. Remember, there's no such thing as a free lunch.
