How much investment does a small real CS need?

Depends on how big you want to be, two or three thousand to hundreds of thousands.

If it is a laser, what is the maintenance? Large venues and scenes range from 80,000 to130,000.

The laser in a small venue or indoors is about 15,000 to 60,000;

I'm not sure about paintballs, but the venue and indoor space are definitely not small. It should be 40 thousand to 60 thousand

Of course, if you want to make money, you can spend another three or four thousand dollars on advertising or group buying in newspapers, and the income will be even greater.

Built in a remote place, try to draw road signs on the road.

That's all. I wish you success!