"Church is just one part of our lives. For most tentmakers, our job is our church, and the work place is our place of worship. All Christians need to grasp the fact that business is a medium of pleasure to God and a tool of doing His good."
Tentmaking: The Life and Work of Business as Missions by Patrick Lai. This book is the bible of tentmaking. Lai has spent decades using business to enter into and plant churches in restricted-access countries. This book examines every aspect of tentmaking and tells stories from tentmakers to illustrate the highs and lows of the occupation. Lai did a survey of all the tentmakers he could find in the 10/40 window and examined what similarities and differences they had and to see if he could find any common characteristics of "successful" tentmaker church planters.
The book defines several forms of tentmaking and gives plenty of pros and cons of each approach. Lai discusses everything: dealing with the government, how to raise "third culture kids," how to do your home furloughs, how to get along with team members, and pretty much every other detail of life overseas. Even if you're going overseas on a missionary visa this book will has some great things to think about.
I give it 4.5 stars instead of 5 because he doesn't publish his survey data so you just have to take his word for it when he talks about the numbers. But the survey results are a very small part of the book.
Lai closes the book by driving home the point that many Christians today make the mistake of separating "secular" from "spiritual," as if some vocations (like professional pastor or missionary) are more spiritual than others (doctors, stock brokers, ship builders, etc.). If you don't believe you can worship God through whatever you do, then my boss would say you inherently believe in some sort of Gnostic dualism where spirit and flesh are completely separated.
Business isn't just some necessary evil, but something that God uses for His glory. We need Christian businessmen to redeem the fallen marketplace whether at home or among unreached peoples. This book gives you some "best practices" of using business to take the gospel where it might not get a foothold otherwise.
I'll hopefully get to meet Lai next month at this conference.