Do: Request a condition report
It doesn't really matter if you're buying artwork directly from an artist or from an auction house. It is recommended to request a condition assessment for any artwork.
especially for more historical works from the so-called "secondary market."
Although there isn't a standard model for condition reports however, there are some common guidelines. An illustration is provided in a lot of condition reports.
This artwork is marked by notes on any markings. Here's an example condition report by Georgia O'Keeffe.
It might be worth it to hire an independent third party to conduct the condition report depending on the item's value. However, this would increase the cost.
Most likely, service will be at your own expense.
Art collectors with an Artwork Archive Premier Collector plan can store digitally the condition reports for their art pieces using the "additional files"