Your bitcoins should only be stored in cold storage wallets after purchase, and transferred out when you want to sell them. It takes less than 10 minutes. Remember, if you don't have the keys, it's not your coins.
Additionally with these you can buy trusted cold wallets with the Trezor and Ledger
https://www.ledger.com/
https://trezor.io/
And also check the supported coin because in different storage only limited support with the coin you want to, also for their trusted resellers world wide you can check here
[1]https://trezor.io/resellers
[2]https://www.ledger.com/reseller
I'm not partnered or a reseller just shares this information for the benefit of the newbies. Also if you don't have a budget yet ideal to use a hot wallet such as the following.
https://electrum.org/#home
https://www.exodus.com/