You didnt state whether you are planning on running team in a tractor trailer,or straight truck.At least one thing in your favor,doing this with your wife will put all the money into one house hold,and that will let you do both the short loads and long ones,as the majority of expedite freight is less than 500 miles.Do to the hours of service,and the dead head involved,these loads will require a team,even though you may think they can be done solo.
Runnning as a H/W team is the best way to enter expediting,whether running a tractor or straight truck.
What we all hate about expedite is the sitting around,as our loads only come when there is a specific time for delivery,most of the time you will pick up late in the afternoon and deliver first thing in the morning.
I drive a tractor pulling company trailer,as there is less competition,most tractors dont sit around as much as straight trucks,but if your going to be in a straight truck,then you will sit around,as there are 3 times more straight trucks than tractors.
If your planning on running lots of miles,this also may not be for you,as our loads wont give you 300000 mies a year like some teams in regular freight do.
As far as a truck its all in what you think you will need,but if it were me,and I was just starting in this business,I would start out driving for a fleet owner,to get my feet wet,and see if this is really what you want,take notes,not all loads are desirable,but for a carrier to keep its customers,they have to take the good with the bad.
hope this helps you a little
good luck