Or by using the worst ever tactic.
The one that ruins this game (and some others that I know :-) )
But if you feel that other managers get an unfair advantage by doing so (and IMHO they do get advantage) then maybe you should consider it too.
This is the so called Daytrading: meaning you buy players in low or moderate price not in order to use them in your team or to train them but to sell them immediately (or almost) for a higher price and get an easy fast profit from it.
There are some disadvantages in that but not strong enough to restrict this menace/degradation. 1st you lose attendance in home court meaning that you lose some money form the tickets income, 2nd when you sell a player that you recently bought you get the 80% of the selling price in first week and getting higher next weeks.
I am really sad that this exists and to mention it but you have to know your options and what advantages other people have.