I've been monetizing data
I've been monetizing purchased data for over 16 years.
I heavily promote PPL(pay per lead...lead generation) offers because there is no credit card required to complete an offer. All a user has to do is fill out a form in order to make money, so conversion rates are typically much higher than offers that require a purchase. I also promote free sign-ups and free trials. Most free trials really aren't free, in that they require the user to pay for S&H. However, when the user is getting something that would normally cost $50-$60+ upfront and they are only paying $4.99 or so for s&h, they can still convert good. I also promote a limited number of offers that the user has to make an actual purchase,. For them to work the product either need to provide some true saving or solves a problem and you can find something similarly local and needs to have decent amount of mass appeal.
The key to all offers is mass appeal...are likely to be of interest to a very large/wide audience, so the potential exists to produce high volume of conversion. Typically the offer is gong to have some form of make, get or save money angle to it or it can potentially solve a big problem the user is having. Regardless what the angle is, the mass appeal factor has to exist.
I'm not going to bother going into the actually mailing aspect, as it is too broad. However, it is far more involved than just getting data and sending it...in most cases.
Assuming you are successful mailing the data, you want to be segmenting your opens and clickers. These are the users that are the most response and that will potentially convert the best. All non responsive data needs to go, so that your mailing less, making more and keeping your engagement up. At the same time, you should be segment your opens and clicker based on the offer type as well, so that your building sub targeted lists.
The above can work with just about any data, fresh / aged, targeted / untargeted, etc... as long as the mass appeal I spoke about exists.You just need to have your mailing costs to be low enough for the type of data you are sending, so that you are at least breaking-even while segmenting or even take a small loss. Because when you switch to just sending the openers/clickers your revenue should rise and make you profitable. Ideally though, you want to be profitable. When I say you want your mailing costs to be low enough for the data, you wouldn't want to take aged / untargeted data and send it with an autoresponder service, as your response will be much lower than fresh/targeted data and the costs too high for the data to support.
Additionally, you can use your opens/clickers to move up the sending platform food chain, as long as they're not generating complaints outside of what is acceptable or creating any problems, so that you can increase your in-boxing ability.
Anyway, monetizing data can be extremely profitable. Everyone I know that is in the business and knows what they are doing, does 6-7 figures. While that is a huge range, much comes down to ones ability to scale and effectively manage the infrastructure that cones with scaling.