Not that it was needed… multiple inspections since show normal settlement and nothing that indicates a sinkhole.I would like to sell the property for fair market value, however I understand that with the “sinkhole” history the house will sell cash only, 15-20% under market value, since owner/occupiers will have challenges getting insurance and financing.Any ideas how to remove this blemish?

They are usually more willing to overlook your blemishes. 

I didn't fix any of the blemishes on the walls.

Leave without a blemish on his credit and receive his security deposit by ensuring I don't have to do a "trash out" If September's rent isn't paid, I'll have to pursue eviction and I won't be assured he'll be out in Oct. 

Well the state had something to say about it LOL. my only blemish vis a vi a state agency in 47 years of doing this stuff. 

Meaning, has there been a series of late payments, financial woes and report blemishes in the recent past.

It will eventually fall off if there is no activity on the debt, but 1-2 decades is a long time to have a blemish on your report impacting your financial future. 

I've been working on that and getting one blemish off of my credit report. 

So its a gamble that a COVID related blemish on my credit history followed by 2 years of perfect payments would be an issue. 

You will need to have a spotless clean title with no blemishes.