Real estate financing is primarily done by lenders with very traditional underwriting practices that don't factor in crypto or avoid it entirely. Even HNI/private banking doesn't consider crypto part of a liquid portfolio. You can go to Interactive Brokers and get a 1.x% rate with 2x (margin) or 5x (portfolio margin) but that's off non-crypto. To get that same leverage with crypto, you can put in a down payment for real estate (20% down) in 5 properties for 5x leverage. BlockFi/Tether etc. make that liquidity possible without liquidation. Feel free to DM me for more conversation on this topic.
Rates are lower on margin loan, and they’re easier to get compared to a proper mortgage (assuming, you know, you have value assets to borrow against)
Rates might be lower but they're not usually fixed. They're easier to get assuming your liquidity is in equities versus crypto or even a stable income. There's a reason mortgage financing is still more prevalent than margin loans despite what you've stated which are inherent benefits.
You say a bank loans money to someone who owns a certain house, but not to someone who uses the money to buy the exact same house?
0: Holder has ETH
1: Holder borrows Tether, provieds ETH as collateral
2: Holder uses Tether to buy a house
3: Holder borrows Dollar, provides house as collateral
4: Holder buys Tether with Dollar
5: Holder pays back Tether, gets back ETH.
6: Holder now has ETH + House + Dollar Dept
If so, why couldn't they lend the dollars to buy the house in the first place? The bank which lends the dollars certainly could make a contract that the dollars only can be used to buy the house?