Do I have to wait for the next epoch?

I don’t know if someone already asked this but… If I “join” in a pool during epoch 250 for example, i will get the rewards from epoch 250 or I will take rewards only from the 251 epoch?

Q: When do i receive my staking rewards?

A: Lets assume you delegated during epoch 200. Untill the end of that epoch nothing will happen.
In epoch 201 your stake is included in the current snapshot.
In epoch 202 your stake may will produce blocks.
In epoch 203, your rewards are calculated and paid out at the end of that epoch. The rewards will also be included in the next snapshot and thus be staked.

https://cardano-community.github.io/support-faq/#/rewards

Cheers,