In REO appraisals, a cost to cure is required on the REO addendum, so obviously, the appraiser makes up a list of repairs or defects and then provides a cost to cure estimate for each one plus a total.
In general, on non REO assignments, an appraiser provides a cost to cure to provide information to the client, and sometimes as a basis for an adjustment, or a check to see if a market derived adjustment makes sense, by comparing it to a cost to cure. Sometimes a client asks for a cost to cure, or the appraiser can add it to report if the appraiser feels it contributes to report development. It is generally added on an addendum.
A real life example, a garage made into a den. The garage door is still in place, but owener put down carpet and drywall inside the non permited den. The appraiser decides that based on codes, zoning, and the fact that garage door is still in place and able to operate, the appraiser decides not to include any contrib value of the den and values the space as the garage.
The appraiser of course always describes and photographs what is there. Appraiser explains that the owner made an illegal interior den out of existing garage, but the door is still in place and functional, so due to illegal use plus door functioning, the space is treated as a garage on report. See addendum for cost to cure.
The appraiser provides a cost to cure estimate of what it would take to retrofit garage back , re, remove the drywall and carpet.
The purpose of the cost to cure is to provide lender or client with information to make decisions.
It can also assist appraiser with making value adjustments, or whether or not to make an adjustment. If the cost to cure the garage, re take down drywall and carpet is only $500, this can indicate to appraieser that the amount of $ is too small to consider adjusting for, and that most buyers based on the small cost to cure would not consider this a major defect. (if the market says different, if for some reason homes with dens in garages sell for 10 k less, or 10 k more, then the appraiser would have to go with market evidence, and state that due to appeal or utility, the market reaction differs from cost to cure. But if there are no comps, let's say with garages made into dens, the small cost to cure could support that no adjustment for defect is warranted)