A lot of the walkthroughs for Safe Haven that I have seen seem unnecessarily complicated. Here is mine:
1. Upgrade toolbench to level 3.
2. Upgrade radio to level 2.
3. Binge spend the rest of your money on machine gun bullets and health pills.
With regard to recruits, always get the recruit with the greatest firepower (with the shotgun guy being somewhere in between the pistol guy and the SMG girl). This should work with at least two SMG characters and one tank (with the baseball bat) character.