Don't sleep on all of the DeFi options gaining momentum. Projects like Celcius and Nexos allow you to stake your BTC and earn interest on it. Nexos and Maker Dao also allows you to take a credit out on your balance to do with as you please!
I actually made a post responding to your initial question! Thanks for sparking some inspiration to write today!
If ther is one rule... stay away from credit! :D
I really don't like the idea of having an exchange/bank of some sort holding keys.