Most hard money lenders take a lien against the property as collateral. If that's the case, there will be evidence of dealing in the public forum. Also, real estate is registered in the county, which puts it into the public forum jurisdiction to begin. If it has any encumbrances, it's public. If it's on the property tax roles, then it's public. For these reasons, one could hold real estate in a public entity such as a C-Corp or LLC and keep a UCC-1 Commercial Lien over the entity with another holding trust. But every hard money lender is probably lending from a US person such as a company or an all-caps-name entity. So that sort of loan, even if the house is not collateral, would constitute minimum contacts.