In dealing with local organizations regarding permanent installations, there is always the question of what is required. When it comes to cable for connecting to the antenna, a purest would calculate the losses associated with RG-213 versus 1/2 or 7/8 inch heliax and then compare the cost of more power and preamps versus changing the feeders to a lower loss variety. There are formulas and calculations, but what are some good "rules of thumb" that can be put to paper.
Quite often the connectors are the big problem. A set of connectors can easily exceed the cost of the heliax for short runs. There is a new type of heliax called LMR which is much cheaper with only a very minor performance loss and the connectors are cheaper as well.
A second rule of thumb, for UHF type N connectors are essential and preferred, but not truly essential for VHF, where in a pinch you can get by with type UHF (PL-259).