If a home is valued at 600,000 today and someone has a first mortgage of 400,000, we take a second LINE up to 100% which would be a second of $200,000 to draw from in the future if need be….
If the house drops to $500,000 in value then you can never get that extra $100,000) that you can get now in case of an emergency….
They don't come and cut your line later due to decrease in prices just like they don't cut your credit card line when your income drops from $100,000 a year to $45,000.