@Jessica G., yes what you're talking about is becoming a Lead Generation provider.
I actually found a way to do this by accident. Several months ago, when I decided I was going to stop doing direct mail for several reasons (cost, management of all the returned letters, time lag between sending them out to hearing from people, etc.), instead I decided to start building my own lead category verticals, comprising of Probate, Pre-foreclosures, Evictions, Violations and so forth; get them skip traced and call owners, instead of mailing them.
It took me about 6 months to build this operation from scratch, because I had to make adjustments on the criteria I wanted apply in each of the verticals (I ended up with 9 channels), figure out how to get this info in the first place, then put in procedures to automate this process somehow (I started off with hiring VAs overseas, which in itself is a learning process, and now with the help of my IT friend who has partnered up with me, is in the process of automating the data extraction process using AI/machine learning).
I started getting appointments, but one thing I noticed when I would go on these appointments were, that:
A) when I would get an appt, I would be excited.
B) The day of the appointment, I found myself saying to myself how much I didn't wanna go on this appointment. Ever been there?
C) Being that this is a seller's market, every seller was (as it has been the last several years) asking wayyyy too much.
But one of my verticals is not a lead source you can just Google, go to their website and purchase, like you can with, say Probate, Tax Delinquent, or Pre-foreclosures. And the prospect to appointment setting ratio is very high, and it's something I can scale nationwide. So it just dawned on me; why don't I sell this data?
So if you're wanting to sell data, you would need to know; what your customers want, if you can gather the data they want, if you can try to automate it, and find a pricing structure that works. I'm not sure what type of lead categories you're working on, but regarding vacant properties, you might want to check out Vacant Houses. I haven't bought their list, but you can see what's available in your area to be more efficient.
Hope that helped.