A pot limit holdem has a restriction with the amount of minimum bet a player can place at a time.  At any point in time with pot limit holdem the amount of buy in should be equal to the then existing value of the pot.  A raise of a call should be existing value of the pot plus the raise. A pot limit holdem is widely played online for play money by many people.  With pot limit holdem seemingly to complicate the loss most players tend to be tight and aggressive and fold most of the time to prevent a huge loss. With such risky variants it is wise to play tight and aggressive until one learns to calculate odds and several of strategies versus table image.