@imfarhad - For my personal experiences, I strongly not recommend any newbie to jump into any Solo Ads Campaign until they have learned and well understand of how things up and go. Because most of the time, the newbies enter into Solo Ads, they probably dream for a quick buck on sale from the mailing list. But they never realize that they are using someone else email list. Yes, you can make some sales to cover the cost and generate some profit or even big profit from other people email list. But at the end you are losing money in the long run in non sustainable way.
Once buying any list from Solo Ads Campaign, you need a well plan to convert those lists to be your own list and know how to warm up those lists to be hot list. As you mentioned earlier, specific target niche list of email may be not that cheap. Whatever it is, the newbie can experience it by allocate some budget to test the market before scale up.
Have a great day. And very much thanks for sharing an interesting topic. !ENGAGE 25