Cheapest way to balance it is to hang your RC with string tied to the center point of each shock tower. It'll be quite easy to see where ballast needs to be added or components moved. On some touring cars, the holes will already be drilled. On my Xray, there are holes drilled in the chassis to accommodate balancing posts.
You can also use a quarter inch square x foot long piece of wood (LHS or Home Depot will have it) to help find the front to rear weight distribution. Slide it under your chassis with the wheels removed.
If you still want scales, search ebay. I bought an 11 pound capacity unit for about $30.