Look the address up in the county assessor's parcel records, which are public in every US county and online in most, and read the owner name and mailing address off the parcel; where the owner is an LLC or a trust, the state's business registry or the recorded deed at the county recorder names the people behind it.
Property ownership is a public record by design: the county assesses tax against an owner and the recorder files every deed, and both are open to anyone. Most people never find this out because the portals do not show it. It takes about five minutes, and it is free.
The assessor first
Every county assessor keeps a parcel record for each property with the owner of record, the mailing address for the tax bill, the assessed value, the legal description and the last sale. Search by address or by parcel number on the assessor's site; in Clark County that is the assessor's property search, and the record shows the owner, the mailing address and the recorded document that transferred it. If the mailing address differs from the property address, the owner does not live there, which is what most people asking this question want to know.
Our own property pages carry the Clark County parcel record for every home we track, off-market ones included, so an address in the Las Vegas valley can be looked up here without learning the assessor's interface.
When the owner is a company or a trust
An LLC as owner is common for rentals. Search the LLC in the state's business registry (the Nevada Secretary of State's SilverFlume for a Nevada LLC), which lists the registered agent and, in most states, the managers or members. A trust as owner names a trustee, who is usually the person; the recorded deed at the county recorder may show the trustee's name and the trust's date. Out-of-state LLCs registered in Delaware or Wyoming can be opaque by design, and the registered agent is then the only public contact.
The recorder for the history
The county recorder holds every recorded document against the parcel: the deeds in order, the deeds of trust (mortgages) and their reconveyances, liens, and notices of default. Searching the recorder by parcel number or by name gives the chain of ownership and shows whether the current owner has a loan, how much it was for, and whether they are behind on it. Notices of default and trustee's sale are recorded there too, and they are what our foreclosure pages count.
A title company will pull a full chain for a fee, and a real estate agent can often see the owner in the MLS's tax records. Neither is necessary for the basic question.
Questions people ask
Is there a free way to find out who owns a property?
Yes. The county assessor's parcel search is free and public in nearly every county, and the county recorder's index is free to search in most. Paid people-search sites resell the same records.
How do I find out who owns a property if it is an LLC?
Search the LLC in the Secretary of State's business registry for the state it was formed in. Most states list the managers or members; all list a registered agent, who accepts mail for the company.
Can I find out how much someone owes on their house?
You can see the original loan amount from the recorded deed of trust at the county recorder, and whether it has been reconveyed. The current balance is not public; it is between the owner and the lender.