Chong,
Good for you! And good luck.
The 'biggy' seems to be how big or small radios are now. Newer ones tend to be smaller than older ones. Big deal, till you start to try to find a place to put them in a car. Or in the house, trying to push just -one- button at a time! (<-- my problem).
Probably the 'biggy' with used stuff is just how 'used' is it and how old? After a certain 'age', finding parts gets difficult. After a certain amount of 'usage' they're beat to death'. Staying away from those thingys is sort of a good idea.
I'm not much of an Icom or Yaesu fan but can tell you a bit about the Kenwood stuff, sort of. If you add a TS-450 and TS-850 to "dxhound"s list you've pretty well covered Kenwood for the last 20-30 years. And no matter what model or brand you select, it doesn't say anywhere that you are 'locked' into that choice forever.
Have fun!
- 'Doc
PS - The common saying, "If you ain't got Kenwood you ain't got squat", is incorrect! It ought to be, "If you ain't got Kenwood, you got squat!". I'm sort of prejudiced.