Speculation - This one is a bit harder, and I've used short term loans to make money. You need to watch the interest if any, and you need to be able to cover any losses if they happen. Examples are - running a business with a 30 day credit line, and using the credit to supply corporations.
This is very different to what most people here would think of as "speculation", which is taking a loan to buy bitcoin or some other coin to trade with. Incredibly risky, and not recommended.
Your house - You should be able to negotiate a very low interest rate for this type of loan, and it can make sense if the repayments including interest are less than you would pay for rental.
Even if your mortgage repayments are higher than they would be if you were renting, it can still be a good financial decision. If you rent for 30 years you have literally nothing to show at the end up of it except money down the drain. If you pay a mortgage for 30 years, even a slightly more expensive one, at least after 30 years (for example) you own some property, which is usually quite a good store of wealth. That's not to say you should put up with an expensive mortgage though - always shop around and haggle for the best price.