I still don't understand how you pay back the loan. You would have spent all that fiat for living expenses. So then you need to sell BTC in the end.

Can you roll these loans over at the end of the term? If so, when is the interest and principal due?

You sound like Mashinsky with his magical flywheel. So every year you refinance the old loan with a bigger new loan. You know the music won't stop because it is your own company lending you the money, and you have a huge stack of BTC to survive large drawdowns. For an average Joe with small BTC stack your strategy is very risky. You just shill your lending outfit to degen folks.