The real 'not best practice' here is attempting to learn what could very well be safety critical basic information from a salesman.
At least now we know why it was for sale.
The gun should not double. Either trigger should function independently.
This could be a result of the 'inexpert' stocking job, or a byproduct of the reassembly after refinishing, or a host of other things from simple to correct to a fix requiring the hand making of one or more parts.
I'll not comment further on the ethics of some engaged in the 'sport' of commercial business, but I will caution you to slow down and conduct a course of self study on this whole firearms hobby.
The first stop could very well be the club at which you intend to engage in your chosen sport. They may have a QUALIFIED instructor, or perhaps a mentoring program. You likely can at least ask questions and observe. Most of these places are interested in growing their sport, and doing so safely.
