In my county I can look up everything about a property on the county property tax appraiser's web site. I would expect chances of you being able to that are fairly good.
You should be able to get the donor's cost basis at your local property tax appraiser's office. If the property was originally purchased by the donor prior to 1980, chances are 50/50 you will find the information online. But if you visit the property tax assessor's office, they should have all the information you need, including what was paid for the property when the donor originally purchased it, since the buyer had to pay transactional taxes based on what they paid for the property.
Take note that tax values should not be used as a cost basis, as those values assigned by the county property tax appraiser are generally 30% below the real market value. Besides, the tax value for 2022 is probably significantly more than it's tax value 35 years ago, and even more than what was originally paid for it by the donor 35 years ago.
Bottom line is, you need to be able to substantiate your cost basis if ever audited on it. Using the assessed tax value is frowned upon unless you can prove you tried every other means possible first, to get whatever value you're required to use as cost basis for reporting the sale.
I've never heard much about the IRS checking this out. But I myself am not willing to test it. 🙂
