Allowing Players to freely trade Resources makes a Game fun. But that encourages Farming & Bots, specially if those Resources can be sold in a Black Market for real Money. In my Game that is a total Spoiler. In my Game resources are everything. I am developing a Sports Manager Game where the 2 Resources available are Players and Money. In an MMORPG, even though lots of Gold will help you out, you still have to grind and to explore to build up your Character. In my Game once you have excelent Players is pretty much Game over from the building up Point of View. The only Task left is Tactics. The problem is that you can get to this Point quickly by Farming or acquiring the Players and Money from Farmers. You cannot directly transfer Money from Team to Team, but you can pay an unreasonable Amount for a Player, which is basically like transfering Money. I was thinking of allowing PvP Player trading in my Game only for paying Users. Of course that by paying you will still be able to farm, but at least you are giving some Money to the Developer of the Game. I am scared that no PvP Trading will remove the Fun of the Game for Free Users. Any other Ideas on how I can solve this Problem?

How about a recommended price based on skill stats? Price paid can only be withing a certain limit of that. Its not brilliant buts all I could think of atm.

Could you give a little more detail about how new players are added to the game universe? I think that this may be key to finding a solution to your problem.

Is there a fixed pool/roster of players which users can trade? Are new players manually/automatically added to the pool as the number of users grows? If new players are automatically added, is there some random factor which determines the skill level of these players?

Depending on how this all works in your game, maybe an option is to have players take some time and considerable effort nurture and "train up", with some uncertainty about how skillful they have to potential to eventually become? This may make efficient farming impossible.

Perhaps you can exaggerate how quickly players lose skill after they have reached their peak? This means buying a team of top players is only a short-term benefit.

This is a Soccer Manager Game. I was trying to be as Abstract as possible because not everyone likes Soccer and because it can be applied to any Collective Sports Manager.
As in other Games of the Genre Players enter the Game by appearing in the Youth Team of the Users. All Users start with the same Number of Slots for Youth Players. Slots are always full. When a Player turns 19, if he is not moved to the Main Team he vanishes from the Game, leaving an empty Slot that is immediatly filled by another Youth.
Leveling up Players takes Time of course, but unfortunately there is not a lot of Micro Management you can put in Player Training. Typically in these Games you either click a Button that says "Train" and then come back the next Day to see the Report, or like in Eve, you set which Skills you want to train for each Player, and the Player trains continuously, without the Manager having to log in.
I think I found a Solution. If I decide for the continuous Training Model, I will make it hard to Figure out which Skills a Youth can develop better. This adds some Micro Management because you have to constantly change the Training Settings until you find the right Combination.
If I decide for the "Train" Button Model I am going to put a sort of Captcha which takes some time to solve, so even if you have Multiple Accounts, there is a Limit on how much times a single Guy can click the "Train" Button. This also deals with the Problem of the Click Bots.

A lot of clubs have thrown big money around and bought a load of star players, but they don't necessarily work well together. Players also don't generally work well together without playing together a lot. This is why national sides frequently seem to be rather less than the sum of their parts. Perhaps you could reflect this in your game.

Also, give each club a full history that is publicly available. If anyone starts botting on a large scale, their tactics will then be dissected in great detail by the community who will then work out how to beat them. Without being able to win games, they will make less money.