But their market values drop to about 20% when the new season starts. And what if there are a lot of suitable players for you in the transfer market at the start of the season, but you can't bid for most of them because you don't have enough money. You will have to wait until the listing time for the ones your put on the transfer list to end, but then, by that time, the suitable players you have identified will be probably gone too.
This depends on your level also. At higher levels, virtual money does not seem to be a problem, but at lower levels, it is more likely to be among the main limiting factors. Also, at lower levels, negotiations are disabled.