What happens when collateral is in excess of the loan?

[Benjamin Cowles]

If you use hard money for just a portion of a purchase or say the rehab costs would they use the entire property as collateral ? Or in general is there a way of minimizing your collateral to only what would be necessary to recoup their investment so if they had to foreclose on you they wouldn't end up with say a 100k property for a 50k loan? How does this work?