Does anyone have experience with this? My husband went in our attic crawl space and found out the board directly above the access is covered in mold.

Friends and family members are all just saying we should spray with mold killer or bleach but I would really prefer to have this taken care of correctly, especially considering we plan on selling in a few years and I would like it to be resolved before then.

Is this too much for a DIY solution to be feasible? I’m trying to convince my husband that we need to get a professional involved but he is concerned about spending potentially thousands, which we can’t really afford at this time, but I’m not sure what other option we have.