You also might want to check with your insurance person about product or personal liability insurance. You never know how stupid folks can be till they hurt themselves in something you built or repaired and then you find everything you have worked for at risk. That is one of the benefits of an LLC. Possibly you have a friend who is a lawyer, or the internet can be a big help in this area also.

When I went in business for myself 30+ years ago, if I had known all the possible pitfalls just liability wise I might have thought twice or even more times.. Ignorance can be bliss though, at least for awhile. It is a wonder in this day and time anyone wants to take the risk anymore, even with something that seems so simple as you are thinking about.

Not in any way trying to discourage you, in fact the opposite, but it is always better to know going in to something how to prepare and protect yourself from someone doing something stupid with something you built and sold.