That seems like way too strong of an effect to have a land with no activation cost. Generally such abilities that can generate card advantage need to quite overcosted because if you have an effect on a land that produces mana the opportunity cost for that is very small compared to the usual of reserving a card slot for a spell in your deck. For example Memorial to Folly, Memorial to Glory, Gates of Istfell. With an effect like this, I would except it to have some sort of an activation cost along the lines of or .

Thanks for your comment, I'll mark it for review. It's sort of an exalted counter, but considering it doesn't even need to target, it needs to have a cost.