Being a bus driver, I get to chat to a lot of elderly people. One in particular seemed to be quite knowledgable on FH and told me that the best subscription website was:-
I don't know about legal, but I entered a name for UK Naturalisation from the Immigrants board, and just got a list of fees, starting at $30 for one year's access.
Bob
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Searching for Coleman, Moore, Kallnung in London; Margulies, Remenyi in E. Europe; Ancestors of Hessie Stevenson-Coleman-Baxter (Ireland, 1861) and, of course, any other ancestors for my web-site.
I would think they operate similar to credit agencies - if you buy something on "No interest terms for 2 years" or whatever, it is run by a credit company & they instantly check if you are a credit risk. I think it's legal - but probably expensive because they would be accessing data bases that cost to access - when we traded in our last car, the first thing the folks selling us the new car did was access some type of data base to determine if we owned the car, or someone else had a debt owing on it. If you buy a car privately, you can do the same thing - for a fee.
This site presumably has a collection of such data bases to check, based on where you live.