Wow. Lots of questions, and no one has answered you. I'll give it a shot.
Is a players best / preferred position up for debate?
Yes. Position your players based on their skills (i.e., you may have a Small Forward whose skills make him your best Point Guard)
Simple example - I read that in real life the skills for a Center should be Driving and Rebounds... is it wise to obey the positions given to the players or wise to experiment?
It's wise to experiment. The game is rather new, but the general consensus is that Centers need Rebounding, Shot Blocking, Inside Scoring, and Inside Defense.
Secondly transfers... does it cost to list someone?
No. List them as many times as you wish for free. There are also no agent fees, last club fees, or mother club fees.
Three.... are the players you start with worth Transfer listing or just sacking? At what DMI or skill level are they just worth chopping?
Since DMI fluctuates with practice, it isn't the best indicator of a player's quality (or lack thereof). A player's weekly salary is a better indicator of his overall skills, but you must decide which of your players are best suited to play in each position. Guards tend to need outside skills (Jump Shot, Jump Range, Outside Def and Handling), Centers and Power Forwards need inside skills (Inside Shot, Inside Def, Rebounding and Shot Blocking) and Small Forwards need a mix of both. All players need Stamina and Free Throws (though inside players seem to take more FT), and all players can use Driving and Passing. It is up to you whether or not your players are worth keeping, selling or firing.
How do you ensure everyone gets the 48mins... do you leave this to the coach or is this something i must juggle to do?
You must juggle. ;) In a few weeks it will be second nature.
Lastly- money..... how quickly does an average team start bringing in respectable revenue? ie When can i go buy players 20k-50k??
If you've just started, you should be getting a 50k/week newbie bonus. That should give you some room for errors to figure out your finances as you see how much you make from home games, merchandise and the cup vs. what you're spending on players and staff. And I'm not sure I understand the second part of your question, as you can buy players anytime you can afford them
Hope that helps!
-DJ