Yep, it really depends on what you can find. Gotta remember that the higher the level, the higher the staking requirements are. Of course, it's in proportion to the max level of the card.
38/38 Max GF Common (2,000 PP) would need 10,000 DEC staked.
4/10 GF Epic (2,400PP) would need 4,000 DEC staked.
You have to study what works for you. Just because I do it doesn't mean you have to do the same thing.
Also, as a general comment, DYOR whether buying or renting would make more sense.
Plenty of ways to approach the land game. 🙂
I second what @mochilub said. Who knows when the owner of the rental will cancel on me?