Ok, first, i was speaking of rental property.

A rental property is an asset.
Your house is your biggest liability (not an asset)

Your mortgage on your house is your biggest liability.

If you have enough money to buy a house (as a rental):

1. Buy one house, all cash. Get $1,000 per month rent.
2. Buy ten houses, 10% down mortgage. Get 10,000 per month rent minus mortgage payments of $6,000. (interest is really low) = $4,000 per month

Banks lend money via fractional reserve lending. Thus, it is making money out of thin air. And, as a land lord, you can take advantage of this money out of thin air by being on the receiving side.