First, if you buy a foreign patent and produce it abroad, you need to go through the formalities of change at a foreign patent office; This situation is different from other countries, and the treatment process is different; Need to find a foreign institution to handle it.
2. If foreign patents are used in China; If this patent is not patented in China, you don't need to buy it. Patents are not protected and anyone can use them.
Third, if you just want to hold it, you can also sign an exclusive license contract with the patentee and file it in the patent office; After the application, only you can implement this patent; The patentee may not implement it.
Buying a patent is to change the procedure of a patentee. The patentee may produce or use the product or method in the patent.