My opinions aside, do you have a lot of round dial experience?
I flew the -80, but never the 9, no real interest. But prior to the -80 I had a fair amount of experience in GA aircraft flying round dials, though directly before the -80 I flew RJs for a few years. It can be a tough transition as the scan is quite a bit different. I'm not sure about required flight times though I know the washout rate on a DC-9/MD80 is generally higher than most RJs I'd make sure you are ready to make the jump.
Don't worry about buying a type, your employer will pay for it.
I haven't flown for any of those airlines, but the cargo life can be tougher with all the red-eye flying. I know Everts had/has more of a two week on two week off type schedule and you are home based. They should airline you too the airplane and Evert does most of their flying out of Texas and Alaska. USA jet and Kalitta Charters I think you have to live in YIP and be close to the airfield with a short call out I think? But that may have changed with increased demand. There are some threads on here with guys discussing working at those places.
As for the pay? No it's not very good relative to the equipment. On demand charter and ACMI never really pay great though compared the mainline carriers but of course it's not as hard to get hired by them either. Honestly you'll probably make more money and get more time off at Envoy or Endeavour. Especially considering all the bonuses and tuition reimbursement the regionals are paying now. On top of that you'll have a quick upgrade and a flow for interview at a mainline carrier. Okay did give you a little bit of my opinion there.
Good luck.