Most counties (or equivalent) have web sites that include the Recorder of Deeds office. Search for "Deed of Release".
Depending of the search fieldsyou can narrow a search by subdivision or legal description. Know the area you want to invest in, you could enter the first part of a legal description, say souther Hills Block and see what pops up. From there look at deeds of trust and select those filed years ago. If nothing else was filed on those properties in recent years, they have equity.
You might find a "list" somewhere, but guess you'd pay for someone else doing this for you.
I suggest that new investors do some of this leg work themselves so you learn how to do it.
Relying on RE sites and buying lists everytime you turn around means that you won't really learn RE, what you'll learn is how to buy lists.