Piston pay is the lowest and jet is the highest because of the responsibility that comes with both, either in the value of the cargo or the value of the equipment that you are operating. You hurt a Piston engine most your out is 40K, you hurt a PT6 your looking at well over 100K, etc.
Upgrades are a matter of base selection and luck. Do you want to assure yourself of decent upgrades? Be open to the possibility of moving around, maybe not a complete base change but to the possibility of taking an outstaion that comes open from the base your at, not all outstations mean having to move either, some of them are commutable but your QOL degrades very fast and definately downhill. If you choose the base right and don't take some of the more senior bases where there is no to little movement you can make good money fairly quickly. Senior bases that I know for a fact are BFI (haven't seen hardly any movement in the last year) PDX (slowly moving, bottom half of seniority list in the piston moves fairly quickly, turbine.. not), PHX (getting rid of an influx of pilots, still currently no movement, a year ago fairly decent upgrades from chieftain to 99), etc. etc. SLC and possibly BIL seem to have decent upgrades and start in the turbine stuff, other bases still have slow upgrades currently but most of them will dual qualify you in the 99-navajo.
