I think the best approach here is to let them have it, the goodwill will be worth way more than the dirt- the intent is for my daughter & roommates to occupy the house for a few years, then I will decide on keep or sell. 

Works well for me I have a 4-plex there (ONLY because a daughter living in one unit) so it's a write off to visit my kid (one of em) That said I highly recommend real estate.

Our old neighbors were visiting their daughter's family across the street. 

Hello, this chicken-$hit homeowner has decided tom let his daughter talk him out of selling the house to me, we've already decided to wholesale it...

Sure enough his daughter who wasn't there to help him with his mortgage, bad tenants, backed up taxes, now convinces him he can get more for the property as is.

May 1st was day they had to be out by.2nd floor has 3 adults living there: Tenant A (Mom ~50 yrs old)Tenant B (Tenant A’s Brother ~50 yrs old), Tenant C (Tenant A’s daughter.)

This once was a calling where an appraiser had son or daughter taping a house to learn the trade, not so much today.

I had the daughter's info as he had been failing and she paid rent for a few months while they cleaned everything out.

It's not unusual that a couple might bring a friend or relative with them during a viewing but in this case the deal was mom and dad, the married daughter and her husband and one child were interested in renting together. 

If it's their daughter, call the next one.