At this point just buy the damn base, a depot or a gas station should cost around 70 or 80k, and a measly cave should be around 60 or 70k... an outpost around 300k or so. If you dont like the prices right now, you should have been around when a hummer used to cost around 120k
Massing caps is very easy, just farm khan raiders a couple days and you should do enough caps for it, hell just farm miniguns from unity and turn them into avengers and sell them, it would take less than 2 hours to get upwards to 200k