So when I first got into running passive mobile apps (also referred to as Beer Money apps), I found the hardest part to swallow was the up front cost of getting the mobile devices. We all have probably a spare or two laying around these days. However, to actually get enough devices to generate enough apps earning at one time to really make it worth your time was a gamble. You never knew what phones worked best. You didn't want to buy devices for something you weren't quite sure would pan out. (Again, you were just starting out without the experience.) And you didn't want to have to wait very long to get a return on your investment. One day I stumbled upon a way to actually get a free device each month. I am a Straight Talk subscriber and had used their auto pay for years. When I went looking on their site to potentially buy a new phone, I noticed that they actually have free options on their site if you purchase a monthly service card along with it. I got to thinking. Since I am using the service anyways, I would be getting these phones essentially for free as I was going to buy the cards anyways. My wife also uses their service, so I ordered one for each of us. They even had free shipping. I've probably gotten 12 phones or more doing this over the last couple years. 

Caution though. If you do it too often in too short of a period, they may flag you and block you from ordering from their site. Anyways, it is a great way to get a small farm going. 

You should also check out this post: Earn with Swagbucks on mobile devices