How to test the motherboard and percent when buying a BU?

Question

Iron

Good day to all! I found an ad at a local flea market for the sale of a pentax g4600 and an Asus Prime B250M-K motherboard at a very low price. Roughly speaking, the motherboard as a gift. All together for the price of hemp + $10. I called the author, he is not against all possible tests, said the motherboard and the percentages were not really used (intermediate option). Tell me how to correctly check the motherboard and percents so that later there are no problems with them
Thank you all for your help :-)